"In a copy of a book that Colum McCann signed for an auction of first editions, beside the disclaimer that is always printed proclaiming that the book is a work of fiction, the names, characters, places, and incidents are the product of the author's imagination, or are used fictitiously, and that any resemblance to actual persons, living or dead, is entirely coincidental, beside this McCann wrote simply, 'Bullshit'" (James Salter, The Art of Fiction, p. 38).Then again, you don't want to be sued, do you?
"Books that are deemed important weren't written to be important, generally. They became such. I can't think that The Catcher in the Rye was written as an important, life-altering or significant book. I believe it was simply heartfelt. To Kill a Mockingbird doesn't bear marks of an intended importance although I don't know what Harper Lee actually felt. Fitzgerald thought all of his books were important. The Great Gatsby was a short book, only 214 pages, and he was insistent that the publisher sell it at the same price as his longer ones" (Salter, pp. 42-43).
To Kill a Mockingbird is still widely read, its so-deemed greatness still afloat, but it is "a book for children" (as Flannery O'Connor said).
As for The Great Gatsby, this book has claims to being the Great American Novel; it should be sold at twice the price of any other book.