Ultramatic said:
The Odyssey, by Homer. Everything about it is just so... Epic.
I read that as a kid, and enjoyed it's adventure a lot. I recall Iliad was more epic, but it bored me, and I don't think I've ever finished it.
There are so many books I like, and as I like them different ways, it's hard to decide, but here's some books I love and have read several times, and can enjoy again and again:
"Crime and Punishment" by Dostojevski. I like most of his work, but this one is the first one that got me into his stuff. I had read one of his humorous short stories before and didn't like it.
"Scanner Darkly", by Philip K Dick, also "Do androids dream of electric sheep?", "The clans of Alpha moon", there are many books by him I love.
"Grim reaper" By Terry Pratchett. Again, I enjoy all of his books and love most of them, but this is my favourite.
There are a lot of others, but these came to mind first.