The following is a short list of good books couples find helpful. I encourage all couples to pick up a book on relationships and do some reading and talking together in a way that works for you. It can help create a common language to talk about your relationship while inviting you to experience yourselves and your relationship with some new perspective. It's also good to be talking about your relationship in some intentional ways when things are good, rather than just when they aren't going well.
If you are intentional in your relationship on a regular basis you can dramatically increase your sense of connection with each other and it makes the "other" conversations so much easier.
Hold Me Tight by Sue Johnson
The Seven Principles for Making Marriage Work by John Gottman and Nan Silver
The Relationship Cure: A 5 Step Guide to Strengthening Your Marriage, Family, and Friendships by John Gottman
The New Rules of Marriage by Terrence Real
Sexual Intelligence by Marty Klein