Here are some books that I've read and now recommend, or de-recommend. Your tastes may differ. If no author is listed, either the book itself does not list an author, or the authorship is more complicated that I feel like reproducing, or I forget the author :)
[A note: I believe nothing ruins a good book like being forced to read it. That's why I'm calling this list non-required reading.]
Recommended
"Dan'l Boone On the Caroliny Trail" -- this was the first book I read, so it sticks in my memory.
"Tom Sawyer," "Huckleberry Finn," "Life on the Missippi" (and probably everything) by Mark Twain
"Catch-22" by Joseph Heller
Anything by Philip K Dick
"Atlas Shrugged," "The Fountainhead," "Anthem," "We the Living," and anything else by Ayn Rand. Sure, some of it may wear on you after a while, but the sense of life is right.
"Venus on the Half Shell" by Kilgore Trout
Any of the Dave Brandstetter mysteries by Joseph Hansen.
likewise any of the Miss Pollifax mysteries by Dorothy Gilman
likewise still any of the Rabbi Small mysteries by Harry Kemelmann*
"The Lord of the Rings" (and "The Hobbit") by J.R.R. Tolkien
"The Richest Man In Babylon"
"Zodiac," "Snow Crash," "The Diamond Age" and "Cryptonomicon" by Neal Stephenson. I think Stephenson is the greatest living English-language writer.
Anything by JRR Tolkein
The autobiographies of Ben Franklin, Abbie Hoffman, Yukichi Fukuzawa
De-recommended
Anything by Michael Creighton
Anything by Robin Cook
Anything by Scott Turow
*If you get the feeling I like somewhat-cheesy serial mysteries, you're right. Tony Hillerman, Michael Nava, and various other authors get me hooked fast;)