I tend to steer clear of the thick reference books and go instead for books that give me a look into how smart people think about programming.
I have a soft spot in my heart for books that are way too long. But Jesse’s on to something, I think. The problem with big Unix books is that they are tomes of arcane rites; most of it just isn’t relevant to those building systems on a modern Unix (Linux) with modern tools (Java, Python, Ruby, etc.).
Jesse’s way of learning you a Unix is way better, honestly. Read concise programs, cross-reference them with manual pages. Try writing your own stuff. Rinse. Repeat.