I'm gonna assume 'books' means either novels or short story collections - I'll exclude plays and graphic novels, partially because it'd be way too much to choose from then.
This is very difficult. It kind of varies with my mood. But I guess for right now it'd be:
1. The Outsider/The Stranger (depending on translation), by Albert Camus - though the rest of the list varies, this has consistently been my favourite book ever since I first read it. There's something beautiful about the way this book is written, and it's incredible the way it makes you completely understand and sympathise with a remorseless murderer.
2. Dubliners by James Joyce. A collection of near-perfect short stories about... well, about pretty much every emotion you can experience in life.
3. Invisible Monsters, by Chuck Palahniuk - really weird novel, but really beautiful. And damn funny too.
4. Frankenstein, by Mary Shelley - I've had to read this book SO MANY TIMES in English Literature, and I still find new things in it each time - that says a lot about such a short novel. Similar to the Outsider in that it truly makes you sympathise with a character whose actions are truly horrific.
5. Flowers for Algernon - I only read this one recently so I can't exactly judge how I'll feel about it in future, but for now I think it's completely incredible. Almost certainly the saddest book I have ever read in my life, the only one I can ever remember making me cry. Just... beautiful.
Honourable mention goes to God of Small Things, Notes from the Underground, In Search of Lost Time, Hitchhiker's Guide to the Galaxy, Do Androids Dream of Electric Sheep?, Moving Pictures, Harry Potter and the Half-Blood Prince, and Foundation.
Oh, and some stuff I would've included had I thought the list was meant to include slightly different mediums: The Sandman, Watchmen and Hellblazer (comics), the poetry of Charles Bukowski, Krapp's Last Tape and Hamlet (plays).
EDIT: OH MY GOD I KEEP ADDING STUFF SOMEBODY STOP ME ADDING STUFF
Yopaz said:
3: The Wheel of time (series) my favourite series and only 2 more months until it's all done.
I keep hearing about this series, and how it's supposed to be the greatest fantasy out there other than LotR. I'm interested to know from a fan - what makes it so good? I might give it a try.
NightowlM said:
"Slaughter-House 5" by Kurt Vonnegut Jr. I think it was one of the first books that I really read on my own, without having to for class, that I just loved the instant I finished it. I probably wouldn't love reading as much as I do if not for Vonnegut.
"The Waves" by Virginia Woolf. It's just so beautiful and so sad. It's full of beautiful prose and real depth to the inner worlds of each character. I also really identify with the character Rhoda (though that might not be such a good thing).
"The Trial" by Franz Kafka. A book that seems more and more profound every time I read it. During my first reading, I only paid attention to it as a story and loved it. Then I started seeing things that I missed during the first reading and it became much more meaningful to me, though just as a story in itself I loved it.
A plethora of books by Philip K. Dick. It's hard to pick just one that I could say was my favorite. I just know that after I read my first book of his, I knew that I was going to go read another one, and then another, etc... He just has a unique way of looking at things that other authors don't have.
"The Ender Series" by Orson Scott Card. Even though I have not finished the whole series. I know that even if I don't absolutely love a specific book, I feel like I've still gotten know the characters and the world he created better.
All awesome choices except for Ender. You have good taste (mixed with a little bit of bad taste ;P).