A lot of the books are cheating related but I'll give you my list anyways

*Not Just Friends >Shirely Glass
*How to Help your Spouse Heal After your Affair > Linda MacDonald (very short and to the point an excellent book)
Relationship Rescue > Phil McGraw
Torn Asunder > Dave Carder
Getting the Love You Want > Harville Hendrix
When Your Lover Is a Liar > Susan Forward
*The 5 Love Languages > Gary Chapman (this was simply an amazing book and with a very simple concept. I found both my and my bf's love language to be very accurate [there's an online test too] and as we try to keep them in mind we are creating a much better relationship)
Receiving Love > Harville Hendrix
Forgiveness: How to make Peace with your Past > Suzanne Simon
Why Marriages Succeed or Fail - and How to Make Yours Last > Gottman
The Seven Principles that Make Marriages Work > Gottman

I'll admit, I haven't read all of these yet, but they come highly recommended if I haven't got to them yet. But that might get you started...I think I read half of the relationship section at the book store in the past year. A lot of the books I didn't agree with so they aren't posted here. A lot of the books were sort of "take what you like, leave the rest". A lot of the books might have gotten lost in the blurr of insanity I felt