[smizmiatch]

I found the e-book useful. It doesn't contain too much information that can't be found elsewhere if you look around the PokerTracker forums, but it does compile all of these tips in one place.
The e-book discusses finding leaks, identifying fish, exporting notes and organizing your poker data. It isn't necessary, but if you use PokerTracker and play limit poker, it's a worthwhile investment.