I read multiple books. Getting different perspectives helped me find where I fit, what things aligned with my situations, personality & values.
Not just friends by Shirley Glass
Boundaries in Marriage by Henry Cloud & John Townsend.
How to help your spouse from your affair (a compact manual) by Linda MacDonald.
I'm new to SI (2 years post DDay) and got through them with the hekp on books and a lot of hard work. since being on SI, I also found many good articles in the Healing Library.
If you are of a religious background, I found the articles on Family Life website to be uplifting and encouraging.
Highly recommend the Family Life "Weekend to Remember" marriage retreat.
Best of luck to you,