The subject of the book is the practical use of version control. It’s supposed to contain general wisdom applicable to the activity of using version control, regardless of the particular tools. It also has chapters specific to Subversion, Mercurial and Git (and something called Veracity, which I haven’t used).
I haven’t read it yet. It looks nice though: it has the Mona Lisa with some code superimposed on it. (The code in question looks like it could come from Sink’s SourceGear company. Most artistic representations of “source code” seem to be random snippets of HTML…)
It’s nice to own at least one programming-related book, again.