He read "How to help your spouse heal from your affair" first. It's a very fast read. We were still separated but dating at that time. His comment "I'm already doing most of this" and he really was.
He started reading "Not Just Friends" after DDay 2. I forced the issue. I told him his boundaries were shit and threw it at him with the comment "You need to read this book cover to cover 10 times!"
I read both books after we started dating again so I was ahead of him!
Honestly though, the best thing that worked for my husband was hearing his own words. The day after DDay 2, we sat on the edge of the bed together as I read to him some of the things he had posted on Facebook and Twitter. Comments he had written to porn chicks, real life chicks, random chicks - basically acting like a single guy for years on the internet.
He didn't know I had them with me, so when I started reading them, it caught him off guard. He listened for a few minutes before the tears started. Then he tried to take the papers away and told me to stop. He didn't want to hear "that filth" coming from my mouth anymore. NOW he's very cautious about how he talks to other women.
Good luck with your R!!