It was the first time I read literature on hair typing (I'm a 3a) and saw pics that glorified all sorts of textures instead of addressing how to "tame" them, alternatives to chemical processes, moisturizing processes for damaged hair (mind was at times both relaxed and colored). He discussed silicones and sulfates, and weirdly pushed for Nexxus Humectress conditioner for damaged hair. I was a teenager then, and the book felt so revolutionary compared to other hair care books out at that time. The humectress did save my hair as did his approach to washing the different types. I bought Sam Fine's makeup book shortly after too.
It is probably outdated now, but many of the current naturally curly resources online (for both Black and non-Black women) use similar hair typing and approach, although online forums have helped sophisticate the process more.