You know you might have a book problem when all the librarians know you by your first name...
By favorites I'll assume you mean the ones I keep going back to as opposed to those that were just really good one time reads e.g. Steven Kings "Dark Tower" series was amazing, but having read it once I've never felt the need to pick it back up.
When I feel the need for something heavier:
"Zen and the Art of Motorcycle Maintenance" by Pirsig. I reread it every couple of years and get something fresh from it each time
"The Art of War" by Sun Tzu. Same as above
"The Republic" and "Apology" by Plato
"Gödel, Escher, Bach" by Hofstadter
"The Power of Myth" and "The Hero with a Thousand Faces", both by Joseph Campbell
"The Brothers Karamazov" by Fyodor Dostoevsky, Simply amazing story, simply amazing prose.
Anything Kurt Vonnegut or John Steinbeck
Most anything dystopian, 1984, Infinite Jest, Brave New World, Catch 22, A Canticle for Leibowitz, The Road, The Handmaid's Tale, etc...
When I want something lighter:
Anything by Bourdain, although "Medium Raw" and "The Nasty Bits" are particular favorites.
"The Best of Wodehouse", an acquired taste but the guy can crack me up with just his phrasing.
"The Hitchhikers Guide to the Universe" and "So Long, and Thanks for All the Fish" by Douglas Adams, the guy's a quote machine.
Tom Robbins early stuff (Still Life with Woodpecker, Jitterbug Perfume, Another Roadside Attraction, etc), before he got lazy
Most anything by Pat Conroy. He's probably best known for "The Great Santini" but he's a great example of an almost great author. His prose is just incredibly lush and make his books fantastic reading, but the stories themselves are usually kind of weak, almost like his considers the plot to be an inconsequential framework to hang his language on.
Lots more of course, but winnowing down to a handful ain't easy.
