One little-known book is "Linux for System Administrators (with Notes on Linux Installation)" -- it was written April 2005 by a Seattle community college professor. I took his course, and "the book" (a printed packet about a third of an inch thick) is the one I use most often for reference. It's located, in total, for free at its permalink -

A great deal of the book is involved with administration of a linux install from the command-line. It has some discussion about the different shells and the difference in commands, but almost all the commands are geared toward bash.