There are so many good relationship books available but these are just a few we have read and really enjoyed. (These would be good for women to read too!):
The Magic of Making Up - Travis Jackson
The best selling save your relationship book for 3 years and counting. Practice and very specific instructions for getting her back.
Men Are From Mars, Women Are From Venus-John Gray
This one has been around a while but the principles remain the same. If you want to understand the opposite sex better then this is a good primer.
500 Lovemaking Tips and Sex Secrets-Michael Webb
For every husband that wants his wife to have an experience that will make her say yes to his advances. Nothing racy or in bad taste, but a practical and fun ebook that you can begin using tonight.
Stop Walking On Eggshells-Otto and Susie Collins
This book is from the bestselling married authors that give practical things any man can to to prevent and heal conflicts.
Make Women Laugh...and Fall in Love - Martin Merrill