reading material on IFS

My therapist reccomended that I read a few books by Richard C Schwartz, specifically Greater Than the Sum of Our Parts.

This is the same therapist that told me i only had parts and not DID because I do not have an aggressor in my system.

How much weight do these books hold in significance to the relevancy in modern day DID, and is anything by him worth the read?

She also offered to do IFS therapy with me but i'm a little apprehensive with this therapist in specific, and i'm considering switching to a different one that specializes in it.

Thoughts?