<< Ditto Derango... "Running Linux," a little dated, but still the champion. >>
True, it is just a bit dated, but nothing that it talks about has really changed except for some of the samba stuff and the entire X windows chapter. Other than that, its just basic command line linux. Also "A Practical Guide to Linux" is pretty good, although I can't remember the author of that one. That book features more detail on the "how" aspect of doing things. Its a good companion to "Running Linux", IMHO