Stephanie,
The book link at the top of the site has a list of books:
https://www.malesurvivor.org/Bookstore/index.htm
One the books, Beyond Betrayal by Richard B. Gartner covers all forms of male childhood sexual abuse including mother/son abuse. I have a copy of the book and many others on male CSA and this book would be at the top of my list. It has helped me tremendously as a survivor.