Mastering Linux
Arman Danesh, Michael Jang
I actually still look stuff up in Mastering Linux occasionally, so from that point of view, it was worth it. I also used the CDs and stuff that came with it as the basis of a machine setup at one time, with some help from the book, so even though a bit pricey at the time, it did its job. You aren't likely to need this level of help now though.
