We all know the most popular books for software engineers. One could just google it (e.g., Clean Code, DDIA, SICP, TAOCP, K&R books, Steven's books, etc.).
What are the not-so-popular-but-still-good books in computer science/software engineering out there?
Considering that software isn't just a branch, but a current "engineer's engineering", the more complex, flexible, powerful area, a good software engineer should strive to maintain and expand his knowledge in other areas as well. Physics(actually, natural sciences) and math, and also other traditional branches of engineering can provide a lot of useful material. Search there too.
"Quantum Computing Since Democritus" is a good specific example, I think.