Helping out a friend go through some books on this issue.

This book had a great balance of Christian sexuality and the brain science behind addiction, specifically addiction to pornography (which people argue about whether it qualifies as an addiction, and while women can get addicted as well, it usually affects men in a different way).
For the brain science - see chapter 4.

***Not really recommended for people who aren't Christians - the author is clearly passionate about the subject, and he does get pretty preachy. That being said, I think he does offer hope for the Christian addict (but this is definitely seen more in the end than the beginning). I think the book could've been shorter, but there is some good information.

I do like what he says about sexuality and sanctification - he brings a good biblical balance without saying "sex is everything" or "sex is only to make babies."
He seems surprisingly open when it comes to sexuality - he makes a big distinction between sex and gender, which is really great.