I have gotten a lot of use out of their other books. "Take Control of Your Airport Network" saved me a lot of frustration setting up a network for my roommates, and "Take Control of Spam with Apple Mail" is what led me to buy SpamSieve, so the book deserves part of the credit for solving my spam problem.
So, when I saw that they had a book about backups, I jumped at the chance to get some more good practical advice. Since I already have a copy of Retrospect sitting around gathering dust, I was happy to see a great section dedicated to setting up a recommended backup plan using Retrospect. That section was helpful enough to get me back on track with regular full duplicate backups as well as the incremental backups of selected files I was already doing. That alone was well worth the cost of the book.