A Programmer's Bookshelf
An anonymous reader writes "With christmas just round the corner I have been looking for gifts for my geek friends. But what book? I recently found a simple page with one person's bookshelf and explain what's good and what's not. What do you think? Whats on a programmer's bookshelf? (or what should be and is not!)"
GEB is simply amazing and really makes you think. It is a large tome but it was well worth the read when I read it in high school. It influenced me musically, mathematically and gave me insight to become a computer programmer.
It's a very common book and can be acquired cheaply on amazon, ebay and the wiki.
I also heavily recommend getting to know this site if you're willing to search through lists of books for good deals.
My work here is dung.