While Mac OS X is becoming more and more stable with each release, its UNIX/BSD underpinnings have security implications that ordinary Mac users have never before been faced with. Mac OS X can be used as both a powerful Internet server, or, in the wrong hands, a very powerful attack launch point.
Yet most Mac OS X books are generally quite simplistic -- with the exception of the author's "Mac OS X Unleashed," the first book to address OS X's underlying BSD subsystem.
"Maximum Mac OS X Security" takes a similar UNIX-oriented approach, going into significantly greater depth on OS X security topics: