Best Intermediate/Advanced Computer Science book I'm very interested in Computer Science (computational complexity, etc.). I've already finished a University course in the subject (using Sipser's "Introduction to the Theory of Computation").

I know the basics, i.e. Turing Machines, Computability (Halting problem and related reductions), Complexity classes (time and space, P/NP, L/NL, a little about BPP).

Now, I'm looking for a good book to learn about some more advanced concepts. Any ideas?
The Art of Computer Programming
(Donald Knuth)
The legendary book (of multiple volumes, still incomplete) can't go without mention. For learning about algorithms and their complexities, there is no rival. It's written with practicality in mind, though from a largely theoretical perspective.

(source: wikimedia.org)
The Mythical Man-Month more for software engineering but absolutely one of the best books ever written about programing IMO.