* "Compilers: Principles, Techniques, & Tools" by Aho et al. (i.e., "the dragon book")
* "Data Flow Analysis: Theory and Practice" by Khedker et al.
* "Understanding MySQL Internals" by Sasha Pachev.
* "Transaction Processing: Concepts and Techniques" by Gray and Reuter.
* "Fundamentals of Wireless Communication" by Tse and Viswanath.
* "Genetic Programming: An Intrduction" by Banzhaf et al.
* "Applied Crytography" by Schneier.
EDIT: A few additional comments:
(1) Although these books are problem-domain specific, some of them had benefits outside of their problem domains:
* The Dataflow book has some great coverage of fixpoint algorithms. It's really helpful to recognize when some problems are best solved by fixpoint analysis.
* The "dragon book" takes a lot of the mystery out of compilers. That's somewhat helpful when writing code that needs to be fast. It's super helpful if you want to work with compiler-related technologies such as LLVM.
* Understanding the fundamental challenges of transaction processing helps you avoid massive misadventures when dealing with databases or concurrent / multithreaded systems.
(2) YMMV, but I've found it hard to soldier through these books unless I had a need to for my job or for school.