There appears to be a outpouring of new theoryCS textbooks. I had mentioned the Mitzenmacher/Upfal book on probability and randomized algorithms some time ago. Recently, Jon Kleinberg and Éva Tardos published Algorithm Design, the book with THE MOST elaborate real-world exercises I have seen. Sanjoy Dasgupta, Christos Papadimitriou and Umesh Vazirani have another algorithms text coming out as well.
The not-so-latest addition to this list is a new book on complexity theory by Sanjeev Arora and Boaz Barak. For a long time now, Papadimitriou's book has been the definitive text in this area, but it has begun showing its age, especially with all the new developments in complexity theory. The Arora/Barak book is not yet published, but has been placed online for comments.
The magic of Papadimitriou's book was in making complexity classes spring to life as the denizens of the Zoo that they really are. Complexity theory can be a dry topic if not imbued with a sense of direction and purpose, helping us understand the WHY of how these classes came to be. If my cursory scanning of the Arora/Barak book indicates anything, it is that this new book is a worthy successor.
The two books cover similar material in the foundational sections; where I think the new book takes off is in its coverage of the more "modern" aspects of complexity theory: the profound results on pseudorandomness, hardness and cryptograpy, interactive proofs and approximations, natural proofs, communication complexity and lower bound methods, and even quantum computing.