This one was just recommended to me by my therapist: Dissociation Made Simple by Jamie Marich, PhD. So far it has been making more sense to me than my team in terms of dissociation and parts.

Okay so it isn't a book but it is a set of flashcards! They are called Dissociative Experience Cards by Nicole Black PhD, and can be found at Phoenix Arise Counseling dot Com. There is one deck in the pack that has imagery which might trigger a dissociative experience but does a very good job at showing exactly what it feels like sensation wise, and there's another deck which shows semi-related non-triggering pictures if you're in a headspace that requires it. They are incredibly useful for not only educating yourself and your loved ones about dissociative experiences and what you might be going through, they are also incredibly useful for alters or systems that have selective mutism, go nonverbal, are deaf, or hard of hearing, etc. 10/10 highly recommend

“When Rabbits Howl” is a really good autobiography from the viewpoint of someone with DID

The Haunted Self is probably one of the best books on trauma and dissociation out there. It's the book that introduced the Theory of Structural Dissociation.