My Ex Is Driving Me Crazy: 10 Strategies for Reclaiming Your Life after Divorce

This book was written by a therapist particularly for people who are experiencing backlash from their ex-spouses during or after a divorce, though the advice is also solid for dealing with difficult exes who you weren't married to. Walks you through figuring out and maintaining your own boundaries and safety, coping with guilt and jealousy, dealing with custody and financial shit, and negotiating crappy situations like manipulation and abuse. The book is good because while it's specifically for people with exes who are acting in ways they find difficult, the focus is not on "what's wrong with them" but squarely on what you can do within your own life and mind and locus of control as you get free and build a better life for yourself.