Recently, I noticed that of my programming books only Programming Perl is actually on my computer desk. The majority of my work is done in other languages, but all of those books sit behind me on my writing desk.

Why is it the most useful of my texts? My other books say "Here is a language feature; Here is what it does," or "Here is a problem; Here is how you solve it." The Camel Book says "Here is a language feature; This is why it was made the way it is," or "Here is a problem; Here are several ways to solve it, and ways to think about starting to solve it."

My other books sit behind me because in the "real world" a series of "problem and solution" entries don't often help . The Camel Book has information that I can read and easily generalize to my situation. When I read or re-read it, I feel like I'm always gaining knowledge, some of it not even limited to Perl.

My question is, do you have any other suggestions for me? As far as Perl goes, it and the Cookbook are the only books I currently own. I do a fair amount of work in C, C++, Java, and PHP as well, and consider all the books I have for those languages to be mediocre reference books at best.

What books do you keep within arm's reach?