I found the hacks involving bluetooth, cellphones and your Mac worth the price of the book. Prior to this I "wanted" a bluetooth phone. Now I "need" a bluetooth phone. =) I was also happy to find the info on getting the Postfix Mail Server running.
The great thing about the hacks, IMHO, is that despite there only being 10 hacks or so that you might find useful enough to start using right away, you're bound to come up with another few on your own. For example, by combining what I learned from a few of the hacks, I was able to set up Virex to scan my Mail inbox for viruses every 15 minutes. So far, I've only found W32 viruses, but you can never be too cautious. =)
If you want to feed your inner geek, this book is for you.