I doubt he has a thing for your boyfriend.
I know a few guys who think that book has all the right answers. They're the same guys who already want to not commit and generally play the field for life. There's nothing wrong with that as long as you're up front about it. He probably just thought your dude was in the same boat and he's trying to get him back to that mindset because it's fun to have some one to discuss things with.
It's funny, but not a big deal.
I agree with your assessment. I have another friend who loves this book. This friend is a bit of a...playboy. He also was recently burned by a girl who he thought he loved, so reading this book just fit perfectly into his worldview at the moment.
My boyfriend is firmly a monogamist (we were both cheated on by our spouses and have the same expectations of a monogamist rel
ationship). We both agree that the book is firmly lacking scientific justification and context. BF is a philosopher and has big problems with the way the arguments are laid out. His reading the book isn't a big deal-- it's not like he's going to suddenly change his life based on a book-- but I think it is a big deal that this "friend" is still harping on him about extracting himself from this rel
ationship, granted he's being slightly more subtle now. I'm certainly fed up with it and BF has just about had enough himself.
I don't think that this "friend" is actually after my BF-- those are just amusing jokes. I think the real problem is that "friend" fancies himself to be all-wise while at the same time being terrified of re
lationships because he hasn't had one in 25 years. This person is on the record as saying that he regrets that BF didn't tell him about us sooner so that he could have put a stop to it. Like that would have happened. There's a lot more to it, but the reasons don't matter. He's being a giant jerk and should leave us alone.