Mac OS X Books for Unix Admins?

ikioi asks: "There seem to be plenty of books to help long time Macintosh users acclimate to the new details of Aqua, but does anyone know of a good 'Mac OS X for Unix-Heads' type book? I'd love to have one aimed at unix-admins. Maybe something that talks about netinfo, boot up process/scripts, filesystem details, Apple's GCC extensions, and so forth." For those interested in OSX who may have missed it the first time around, Ask Slashdot has handled a question on books about programming under OS X.