O’Reilly today announced the release of “Mac OS X for Unix Geeks,” a new 7, 395-page book that has been revised and expanded to cover further changes to what is now the world’s most widely-used Unix system. According to coauthor Brian Jepson, developers faced an unexpected learning curve. “Hacking code on a Mac is similar to hacking code on  other Unix systems, but there are subtle differences between the Unix they’re accustomed to and how things are done in Mac OS X,” remarked the author. The book is priced at US$34.95 and is available now.