Start with high-confidence dissociation & did books, then narrow by subgenre or adjacent topics.
The Stranger in the Mirror
Marlene Steinberg, M.D., Maxine Schnall
The Myth of Sanity
Martha Stout
Rebuilding Shattered Lives
James A. Chu
The Dissociation Made Simple Flipchart
Jamie Marich PHD, Jamie Marich
Dialectical Behavioral Therapy for DID--The Workbook
Johanna Knyn