If you have any experience, this book is probably going to not be of much value as it really is a beginners guide. Developers can probably get up and running quicker using the online docs and examples than this book. That said, it could be a good introduction to anyone wanting to get started with online mapping APIs. A sample chapter is available if you’d like to see if this book is for you.
If there is one thing you can say about the Geo/LI space is that we’ve got a great selection of books to pick from lately. This OpenLayers book is probably no exception to those wanting an integration to OpenLayers. People always ask me what technology should they learn (Should I learn ArcObjects?? – Er no!) and I usually say OpenLayers. If you are the type that likes a book to help them learn how to do something, I’m going to say OpenLayers 2.10 - A Beginner?s Guide is a good choice to get your head around OpenLayers.