This is the best book I've seen on the subject. Very well organized and clear. If you're programming Outlook you need this book. Here's a tip. Use VBA whenever possible, rather than the VB Script available on the Outlook forms. The book shows you how to program for events such as the addition of a new item or changing an item. You can avoid VB Script programming on the forms this way.
Before this book was available, I used the Outlook Help files as a reference for objects, methods, properties and events. Anyone who has used the Outlook Help files knows how prone they are to errors, so this book was a welcome edition to my collection. I use it so regularly, that the spine on my copy has already has a crease.