JK Rowling came up with the idea for Harry Potter while travelling on a train:

"I was travelling back to London on my own on a crowded train, and the idea for Harry Potter simply fell into my head. I had been writing almost continuously since the age of six but I had never been so excited about an idea before.

I did not have a functioning pen with me, but I do think that this was probably a good thing. I simply sat and thought, for four (delayed train) hours, while all the details bubbled up in my brain, and this scrawny, black-haired, bespectacled boy who didn't know he was a wizard became more and more real to me."

- as told on jkrowling.com

Inspiration struck for The Hobbit author when he was marking exam papers:

"[I remember] the actual flashpoint. I can still see the corner in my house in 20 Northmoor Road where it happened. I'd got an enormous pile of exam papers there and was marking school examinations in the summer time, which was very laborious, and unfortunately also boring.

I remember picking up a paper and nearly gave it an extra mark, or extra five marks actually, because one page on this particular paper was left blank. Glorious! Nothing to read. So I scribbled on it, I can't think why, 'In a hole in the ground there lived a hobbit.'"

- as told to the BBC in March 1968 

Artist turn novelist Audrey Niffenegger first envisaged her heart-wrenching debut novel The Time Traveler's Wife in the form of images:

"The idea came in the form of the title, while I was drawing one day. I wrote it down and began to turn it over in my head. The title contained two characters, the time traveler and his wife. It seemed that it might be rather trying to be the wife. I imagined her waiting. Then I had an image of an old woman in a bright room, waiting, and I knew that was the end of the story. After that it was a matter of figuring out who these people were, and how that woman got to that room."

- From a 2009 interview with She Knows 

A vivid dream inspired Stephenie Meyer to pen her smash hit Twilight series: 

"I can say with certainty that it all started on June 2, 2003. Up to this point, I had not written anything besides a few chapters (of other stories) that I never got very far on, and nothing at all since the birth of my first son, six years earlier.

I woke up (on that June 2nd) from a very vivid dream. In my dream, two people were having an intense conversation in a meadow in the woods. One of these people was just your average girl. The other person was fantastically beautiful, sparkly, and a vampire. They were discussing the difficulties inherent in the facts that A) they were falling in love with each other while B) the vampire was particularly attracted to the scent of her blood, and was having a difficult time restraining himself from killing her immediately."

- from the stepheniemeyer.com blog

Agatha Christie's world-famous female sleuth, Miss Marple, was inspired by her own grandmother:

"Although a completely cheerful person, she always expected the worst of anyone and everything. And with almost frightening accuracy she was usually proved right. [She used to say] 'I shouldn't be surprised if so-and-so was going on.' And although with no grounds for these assertions, that was exactly what was going on. ...[The character of Miss Marple] insinuated herself so quietly into my life that I think I hardly noticed her arrival."

- taken from recordings made by Agatha Christie in the 1960s

Hilary Mantel woke up one morning with the first line to her Man Booker Prize-winning novel Wolf Hall:

"The title arrived before a word was written: Wolf Hall, besides being the home of the Seymour family, seemed an apt name for wherever Henry's court resided. But I had no idea what the book would be like, how it would sound. I could see it, rather than hear it: a slow swirling backdrop of jewelled black and gold, a dark glitter at the corner of my eye. I woke one morning with some words in my head: "So now get up." It took a while to work out that this was not an order to get the day under way. It was the first sentence of my novel." 

- From an interview with the Guardian, 2012

Khaled Hosseini was inspired to write The Kite Runner after watching a news report based in his native Afghanistan:

"I was watching a news story in the spring of 1999 on television, and this news story was about the Taliban. And it was talking about all the different impositions that the Taliban had placed on the Afghan people. And at some point along the line, it mentioned that they had banned the sport of kite flying, which kind of struck a personal chord for me, because as a boy I grew up in Kabul with all my cousins and friends flying kites.

So I sat down after that news story and wrote a 25-page short story about two boys in Kabul flying kites, and it became this kind of a much darker, more involved tale than I had anticipated.

A couple of years later, in March of 2001, I rediscovered the short story in my garage, essentially, and it kind of became the inspiration for the novel. And I kind of sat down and began expanding the short story into a book, which eventually became The Kite Runner, the novel."

- From a 2012 interview with Radio Free Europe

A war report on TV fuelled Suzanne Collins' smash hit series The Hunger Games: 

"One night, I was lying in bed, and I was channel surfing between reality TV programs and actual war coverage. On one channel, there’s a group of young people competing for I don’t even know; and on the next, there’s a group of young people fighting in an actual war. I was really tired, and the lines between these stories started to blur in a very unsettling way. That’s the moment when Katniss’s story came to me."

- From a 2008 interview with School Library Journal

Arthur Golden spent many months labouring over Memoirs of a Geisha but it took a chance meeting with a real-life geisha to turn the novel into an overnight success:

"Geisha because when I was living in Japan, I met a fellow whose mother was a geisha, and I thought that was kind of fascinating and ended up reading about the subject just about the same time I was getting interested in writing fiction.

Then a chance came along to meet a geisha, which, of course, I couldn't turn down. And she was so helpful to me that I realized I'd gotten everything wrong, and I ended up throwing out that entire first draft and doing the whole thing over again. 

 She was very forthcoming with me. And, truthfully, what geisha don't talk about and what they don't want people to know about is their customers. You know, the men go to tea houses with the expectation that they will have a nice quiet evening and not read about it the next morning in the newspaper."

- From a 1999 interview with CNN

Margaret Atwood came up with the idea of one of her most famous books, The Handmaid's Tale, after dining one evening with a friend in West Berlin:

"One night in 1981, Margaret Atwood had dinner with a long-time friend, unaware that this casual get-together would spark the idea for The Handmaid's Tale.

According to Atwood's own report the two women discussed 'various things as we usually do, including some of the more absolutist pronouncements of right-wing religious fundamentalism. 'No one thinks about what it would be like to actually act it out,' said I (or someone).' Atwood took this very task upon herself."

- From an introduction to The Handmaid's Tale

Kazuo Ishiguro came up with the English setting and protagonist of Remains Of The Day because of a joke his wife made:

"It started with a joke that my wife made. There was a journalist coming to interview me for my first novel.

And my wife said, Wouldn’t it be funny if this person came in to ask you these serious, solemn questions about your novel and you pretended that you were my butler? We thought this was a very amusing idea. From then on I became obsessed with the butler as a metaphor."

- From a 1989 interview in The Paris Review

Mark Haddon, says his idea for The Curious Incident of the Dog in the Night-time first came from an image - and then the story followed:

"It came from the image of the dead dog with the fork through it. I just wanted a good image on that first page. To me, that was gripping and vivid, and it stuck in your head. Only when I was writing it did I realize, at least to my mind, that it was also quite funny. But it was only funny if you described it in the voice that I used in the book.

So the dog came along first, then the voice. Only after a few pages did I really start to ask, Who does the voice belong to? So Christopher came along, in fact, after the book had already got underway."

- Taken from a 2006 Q&A with Powells Books

Roald Dahl dreamed up the basis of The BFG via an idea scrawled in pencil in one of his "idea books": 

"Throughout his life, Roald Dahl kept what he called his 'Ideas Books' - old school exercise books he used to write down any inspiration for a story that came to him. This is how The BFG began - as a note in one of Roald's books, scrawled in pencil, revisited years later and published when Roald was 66. The Ideas Books books are now stored in the Roald Dahl Museum and Story Centre archive."

- From roalddahl.com

PG Wodehouse randomly stumbled upon the character of Jeeves, the long-suffering butler that secured his books worldwide fame:

"I only intended to use him once. His first entrance was: 'Mrs. Gregson to see you, sir,' in a story called 'Extricating Young Gussie.' He only had one other line, 'Very good, sir. Which suit will you wear?' But then I was writing a story, 'The Artistic Career of Corky,' about two young men, Bertie Wooster and his friend Corky, getting into a lot of trouble, and neither of them had brains enough to get out of the trouble. I thought: Well, how can I get them out? And I thought: Suppose one of them had an omniscient valet?

I wrote a short story about him, then another short story, then several more short stories and novels. That’s how a character grows. I think I’ve written nine Jeeves novels now and about thirty short stories."

- Taken from an interview in The Paris Review

SJ Watson got the idea for his best-selling novel Before I Go To Sleep from an obituary he happened to read: 

"The idea came from an obituary I read about a man in his eighties who’d had amnesia as a result of an operation at the age of 27 to try to remove parts of his brain that they thought caused the severe epilepsy that was ruining his life. From the moment he woke up afterwards, his epilepsy was more or less cured, but he couldn’t form new memories.

He’d been treated by the same doctor for decades every week and he didn’t know who she was. I saw a mental image of a woman waking up in a house she didn’t recognise, next to a man she didn’t know and stumbling into the bathroom, looking into the mirror and not recognising herself either. That image triggered the story, was the opening scene of the book and is the opening scene in the movie."

- as told to bafta.org

Ian McEwan used his father's war stories as a basis for Atonement: 

"When I came to write Atonement, my father's stories, with automatic ease, dictated the structure; after I finished the opening section, set in 1935, Dunkirk would have to be followed by the reconstruction of a 1940 London hospital. It is an eerie, intrusive matter, inserting imaginary characters into actual historical events.

A certain freedom is suddenly compromised; as one crosses and re-crosses the lines between fantasy and the historical record, one feels a weighty obligation to strict accuracy. In writing about wartime especially, it seems like a form of respect for the suffering of a generation wrenched from their ordinary lives to be conscripted into a nightmare."

- from a piece in the Guardian, 2009

Maurice Sendak's beloved children's book Where The Wild Things Are drew from characters in his own eccentric family:

"At first the book was to be called 'Where the Wild Horses Are,' but when it became apparent to my editor I could not draw horses, she kindly changed the title to 'Wild Things,' with the idea that I could at the very least draw 'a thing'! So I drew my relatives. They're all dead now, so I can tell people."

- From an interview with the LA Times, 1993

Markus Zusak struggled over his debut novel The Book Thief for years - but inspiration struck when he came up with the idea of death as a narrator:

"Then I stumbled upon the idea of Death narrating the story, and it all made sense. Who is constantly hanging around in times of war? Who would have the opportunity to pick up a story penned by a girl in a bombed German city? Death was the right answer, although there were still a few decisions to be made. 

When I first brought Death into the story, he was sinister. He enjoyed his work a little too much. For months I wrote in this way and again I was falling short in some aspect I couldn’t understand. When I took a break from the book, I was sitting down on the back step and it hit me that Death should actually be afraid...of us. The irony of this was exciting, and it made perfect sense. Death is on hand to see the greatest crimes and miseries of human life, and I thought, What if he tells this story as a way of proving to himself that humans 
are actually worthwhile? At that point, I started writing and I didn’t stop."

- In a piece written for Pan MacMillan publishers

EB White explains how he was inspired to make the protagonist of his best-selling children's book a spider (despite the reservations of his publishers):

"The theme of Charlotte’s Web is that a pig shall be saved, and I have an idea that somewhere deep inside me there was a wish to that effect... One cold October evening I was lucky enough to see Aranea Cavatica spin her egg sac and deposit her eggs. (I did not know her name at the time, but I admired her, and later Mr. Willis J. Gertsch of the American Museum of Natural History told me her name.) When I saw that she was fixing to become a mother, I got a stepladder and an extension light and had an excellent view of the whole business." 

- taken from a letter written by EB White in 1952

John Green was driven to write The Fault In Our Stars after meeting Esther Earl, a teen cancer sufferer whose YouTube videos and blogs inspired millions before her death aged 16:

"I could never have written this if I hadn't known Esther. She introduced me to a lot of the ideas in the book, especially hope in a world that is indifferent to individuals, and empathy. She redefined the process of dying young for me. 

Walking out of the hospital in 2000, I knew I wanted to write a story about sick kids, but I was so angry, so furious with the world that these terrible things could happen, and they weren't even rare or uncommon, and I think in the end for the first ten years or so I never could write it because I was just too angry, and I wasn't able to capture the complexity of the world. I wanted the book to be funny. I wanted the book to be unsentimental. After meeting Esther, I felt very differently about whether a short life could be a rich life." 

- From an interview with Good Reads in December 2012

George Orwell was inspired to write one of the greatest works of 20th Century literature after watching a little boy whip a horse: 

"It struck me that if only such animals became aware of their strength we should have no power over them, and that men exploit animals in much the same way as the rich exploit the [worker]."

- From an interview with George Orwell in 1950