The Seven Principles for Making Marriage Work by Dr. John Gottman. Dr. Gottman has found through studying hundreds of couples in his "love lab" that it only takes five minutes for him to predict--with 91 percent accuracy--which couples will eventually divorce. What he's learned about keeping a relationship healthy and happy is in this book. This is an especially important book for anyone early in a relationship.
Five Languages of Love by Dr. Gary Chapman. This is a fabulous book. It's easy to read, provides real world examples, and, most importantly, gives each of you ways to improve your relationship. Whether you feel its broken or beautiful, Dr. Chapman's insights can help your relationship.
Men and Marriage by George Gilder. A book that Dennis Prager considers one of the most important relationship book he's read. Gilder claims that men will only own up to their paternal obligations when women lead them to do so, and that this civilizing influence is the most important part of maintaining a productive, healthy, loving society.
The Kosher Sutra by Shmuley Boteach. No, it's not about sex - it's about living a curious life within your marriage. Rabbi Boteach's Eight Secrets are the key to reawakening our dormant desires and releasing ourselves from the complacency that has taken hold of far too many of us. What does this mean? Turn off American Idol and find out. Your relationship is worth it!
She Comes First: The Thinking Man's Guide to Pleasuring a Woman by Ian Kerner. There is something in this book for every man. Not only does Kerner 'lift the curtain' on the biochemistry that drives things for ladies, he also gives a number of stats and easy 'how to's.'
He Comes Next by Ian Kerner. Want to truly get in his head and figure out what's going on in terms of sex drive. We both learned a bunch about men in this book. Kerner explains things in interesting and logical ways. If you want to know what is really going on in guys, read this book.