Mating in Captivity - Esther Perel
After reading this book it opened up a lot of sore parts in my marriage. After following though with a few of the ideas and suggestions my wife has said she feels closer than ever, even though the truth from the book still makes me feel doubtful.
My suggestion, read with some caution. It's a powerful and well referenced book with some ideas that you may or may not want to consider as a truths in your marriage.