The DB books obviously, but to get a handle on you as a man and focusing on you I recommend No More Mr. Nice Guy and Married Man Sex Primer. Those are focused on helping you individually and I wish I had read them when I was engaged. You have to literally cut the cord and focus on you in order to truly see what you need to do to improve yourself. It will help you no matter what happens to your M. It's a win/win.
M:35 WW:32 Dated 8 years M: 2 BD 6/12/14 S: 7/29/14 No kids Reconcile: 9/25/14 Moved back: 10/7/14