Sticky Church, by Larry Osborne.
Osborne, lead pastor at San Diego's North Coast Church, accurately diagnoses a problem facing many churches today -- the wide open "back door." To Osborne, the key to church life is not bringing as many people as possible into the church, but keeping them in the church. He wanted North Coast to be more "sticky."
The solution that they implemented, to strong results, was sermon-based small groups. The church previously had small groups, but re-orienting them to be a discussion of the prior week's sermon increased commitment to the groups and to the church. Basing small groups on the sermon made entering existing small groups easier for new attendees. From an educational standpoint, reiterating a message in a different form a few days later should increase comprehension and retention of the lesson.
I can see how this idea could be effective, but I've left the book unconvinced that they are the best answer for every church with a wide "back door." But to the extent that pastors and church leaders consider the unique characteristics of their church, Osborne's book presents a tool worth considering.