Alberts is very often held as the "standard text" (much like Grey's in Anatomy, Atkins in Physical Chemistry, or SICP). I would also recommend "Molecular Genetics of Bacteria" by Snyder and Champness (http://www.amazon.com/Molecular-Genetics-Bacteria-Snyder/dp/...). As you'd expect, it's very focused on Bacteria, but it's current and goes all the way from the basic to the very in-depth.

Edit: Oh! And how could I forget Lodish (http://www.amazon.com/Molecular-Cell-Biology-Harvey-Lodish/d...)? Also very good...