101 Killer Apps for your Pocket PC is a handy reference freeware and shareware book for users of Pocket PC PDAs. It's quite comprehensive, but very application biased. The design of the book is great, and geared toward using a doing rather than learning. For instance when they present the program Repligo (a conversion utility that converts documents to PDF formatted for a PDA), they don't just present the program, they title it 'Put a PDF in your pocket'. This hands-on approach makes finding the right application much easier.

The book is broken into nine main chapters and application categories, from work to leisure to sport, and it covers a lot of bases. This also means that the book doesn't really go into the required detail with some applications, and merely introduces them to the reader. However most applications and trial versions are available on the included CD.
If there's a problem it's that there isn't enough product depth, and I find some of the 'killer-ness' of these killer apps questionable, but the authors have tried their best to cover all bases and it's a as good a place as any to start.