I expected this book to continue the story of the first, but Butler clearly had in mind a much grander scheme for the series. The immortal Doro plays an important part, but his sometime companion Anyanwu is left almost entirely in the background. Instead, the story is told mainly from the point of view of Mary, one of their many descendants.
As an exploration of the concept of the book (and perhaps of the series), Mind of My Mind works well. Butler has clearly thought through some of the practicalities of the evolution of psionic powers. However, the book does less well on two other fronts.
The characters in the book are almost uniformly flat. While there's no need to match the histrionics of space opera, Butler's characters are so understated that they almost seem asleep. Big things happen, but there's very little reaction one way or another. With a few exceptions, everything is described in a distant, almost clinical tone. To some extent, this matched the manner of the protagonist, but it made for less than enthralling reading. At times, it felt less like a novel than a history of how the telepathic Pattern was formed.
Even a history, however, might make some mention of the sociological impacts of this radical change in human interaction. Doro's descendants control hundreds or thousands of 'mutes' (non-telepaths), and the emergence of the Pattern exacerbates the situation. Yet the mutes play a minimal role in the story. There's not even much token mention of their situation - mostly, they're dismissed out of hand. I presume that this was a deliberate choice by Butler to convey the attitude of the telepaths, and the fact that they treat the mutes as chattel, to be used or discarded at will. It's an interesting comparison to how humans treat animals now (which I doubt she intended), and how we sometimes treat other humans (which I presume she at least considered). But because there's no introspection or outside voice to point this out, the point risks being too subtle.
I'd like to give Butler credit for this subtlety - for forcing the reader to constantly be on their guard for the choice between empathizing with likable characters (even sociopathic Doro is likable) and keeping in mind that they're doing awful things. I'm not sure, though that credit is warranted. The non-judgmental tone of the first two books is similar, and Butler could easily have offered more balanced social commentary without hitting the reader over the head with it.
I was interested in the theme of this book, but disappointed with Butler's near-abandonment of Anyanwu's viewpoint. As an analysis of the broad concept of how psionic powers might develop, the series stands up, so far. As a story of individuals and human emotion, it falls short.