There are hundreds, if not thousands of books on Unix and Linux. One of the best, in my opinion,covers the politics and philosophy of the Open Source movement in contrast to the closed source industry. It’s called The Cathedral and the Bazaar.

Getting into technical matters, however, you can’t go wrong with the “For Dummies”, “In a Nutshell”, or “Idiots’ Guide” books.

Another good read, which isn’t really Unix or Linux specific is the essay “In the beginning was the command line” which can be read here: http://artlung.com/smorgasborg/C_R_Y_P_T_O_N_O_M_I_C_O_N.shtml