What's the best computer science book you've ever read and why?

I’m an avid reader but I haven’t gotten very deep into Computer Science yet, so I decided to ask on Twitter to find what other people have read:

What’s the best computer science book you’ve ever read and why?

Some responses:

@objo said The Little Lisper (Called The Little Schemer now)
@julienXX said Why’s (Poignant) Guide to Ruby
@Cerberus98 said Computer Organization and Design
@rsturim said Refactoring
@MarkusQ said A Discipline of Programming
@MarkusQ also said Perceptrons. (I’ll let him slide with two responses but only because of his Ruby challenges.)
@brentrowland said “There was a book on the Forth language with awesome cartoons. Don’t remember the name, but it was my favorite.” (I think this is Starting FORTH).
@ajmurmann said Introduction to Algorithms

The best computer science book I’ve read is The Pragmatic Programmer. It was the book that got me interested in the craft of programming. If you didn’t catch my question on Twitter, tell me what the best computer science book you’ve read in the comments.

Eric Davis