The fourth chapter in Rob Bell's book is on lust. It's a great centerpiece for this book as Bell disects what makes people sin - continually. It isn't the lust, either - it's the willingness to accept what one is told (by your mind, desire, the devil, etc.) as truth coupled by the inability to see that the chosen path does not lead to life - which means it works in opposition to God.
One of the things I love is the way Bell instructs the reader to redirect their (sexual) desire into something much much better. It's a very different approach than that of my "we-put-the-mental-in-fundamental" bible school, where the over-riding approach was duck and cover in the face of anything beautiful. Under that system some relationships and marriages were based solely on finding someone with the same calling as yourself to be a partner with - with little consideration of the beauty in the other person.
Great chapter, insightful and would be a great discussion starter!