I found this book to be very helpful. It looks at the different types of leaver, the reasons why they leave, and how to start communicating with them about faith. It includes interviews with people who have left the Christian faith.
I find it easily accessible as it is divided to 6 main sections reflecting the different types of leaver. This makes it easy to go back to if you want to recheck something when you come across a leaver of the faith that you may be in dialogue with.
If you are pastor who has noticed young people leaving the faith then buy this book. You will find it helpful.