I've read it, so has my husband. He is a recovering sex addict (rSA).
I recommend that sex addicts (SAs) read it in my list of resources for spouses of SAs. (FYI, there is no distinction between "porn" addiction and "sex" addiction, it is one and the same.)
Porn Nation specifically addresses sex addiction.
If you're concerned enough to order this book for him you need to consider the possibility that he's got a problem and needs help. Let me know if you need more info.