I second the Phillip K Dick (also check out Man in the High Castle) and Looking Glass Wars. I'm very surprised nobody has mentioned A Song of Ice and Fire yet. Excellent series, if you have the time. Here's my list:
Cloud Atlas by David Mitchell
Another Country by James Baldwin
Go Tell It on the Mountain, also by Baldwin
Pillars of the Earth by Ken Follett
Invisible Man by Ralph Ellison(?)
I always forget about A Song of Ice and Fire, because I assume everyone has heard of it from the TV show I realise that probably isn't true though.
And I can't believe I forgot about Ken Follett!! His "A world Without End" (the sequel to Pillers of the Earth) is also very good even if it does have a few annoying characters :s
People who say "OMG I LURVE GAME OF THRONES <3 <3" but then you find out they never read the books are the most annoying people ever.
Can't that be said about any show/movie that was adapted from a book?
It's like people who are like "God, I can't stand Harry Potter/The Neverending Story I-III/The Golden Compass/A Wrinkle in Time/Inkheart/The Chronicles of Narnia/(insert other examples here), it/they make no sense whatsoever."
And when you ask if they read the books, the response is usually A: No, or B: There's a book? (In the case of Neverending Story, The Golden Compass, and a few others).
People always fail to understand that a good book, such as the above mentioned, the Ender series, and whatnot always are saturated with character/world/plot information that they're not going to translate completely to film. In the case of Harry Potter, for example, many things were explored lightly, and then cut in later films (Quidditch being part of the first 4 films, then cut completely later despite the importance of it in 5)...or they were cut completely (Ron becoming a Prefect, Hermoine forming S.P.E.W and that playing into the House Elves being part of the battle of Hogwarts, Winky being caught with Harry's wand and being let go, etc...)
Likewise, in the case of The Golden Compass, there were characters that were changed/altered (her father/uncle still being very much in love with Mrs. Coultier, his kidnapping of Roger to power his device), plots such as the importance of Dust were minimized, and so on.
Some movies were more successful in the closeness of the books (I thought The Lion, The Witch, and the Wardrobe was very close to the book), some movies were quarter-to-halfway there (Charlie and the Chocolate Factory was as close as Willy Wonka and the Charlie Factory was, but neither of them were completely true to the story), and some fell incredibly short of being true to the story (As much as I love the Neverending Story I, I can see why Michael Ende was furious with it. I imagine he was foaming at the mouth with II and III since they essentially could be considered making fun of his stories with how messed up they were. Also, two words: Ella Enchanted).
That's why I always tell people to read the book if they didn't like the movie, because the book is almost 99% of the time better than the movie. And if you say you don't want to read the book because you "don't like to read" or just want to wait for a better movie to come out...then that's really your own fault, and you're missing out on a great experience.