This is by far the best book I have ever read on how to lead a small group for Bible study and prayer. If I was training Bible study leaders, I'd seriously think about using it as a curriculum. When I'm next in charge of homegroups, I may well buy every leader a copy and ask them to read it.
Having been a homegroup leader for many years, and been in homegroups or Bible Study Groups in many different churches and CUs, there's nothing especially new or revolutionary in it, but it's an excellent compendium of best practice and training.
I bought it because of the number of recommendations I'd seen from people much more knowledgeable and experienced in this area than me. The recommendations were, of course, right.