One of the most useful books in my technical bookshelf is O'Reilly's Unix Power Tools. I own the
second edition, and I can heartily recommend it. A third edition was released at the end of 2002.
Unlike the many interminable "teach yourself UNIX" books, Power Tools has a thousand pages of useful stuff, rather than endless reprints of manual pages you already have. Best of all, it's mostly concerned with how to do real tasks with the huge array of awkward but vastly powerful tools
that come with your UNIX system. Frankly, I defy anyone to figure out how find works from its (generally rather cryptic) manpage. Additionally, like all the best technical books, it's well written in a light, deft style. Its homepage at O'Reilly is here.
Still, there's a few things that Power Tools doesn't cover. A few that I wish it did (and thus that I had to figure out for myself) are detailed below.