In the Foreward to The Mind Illuminated, the author, Culadasa, narrates a history of the intellectual and spiritual journey that led him to write the book. He also makes at least one extraordinary claim:
There is only one kind of “stuff,” and both mind and matter are mere appearances. When looked at from the outside, this “stuff” appears as matter, and as such has been the object of scientific investigation. But when examined from the inside, this exact same “stuff” appears as mind. Non-duality, as realized through direct experience in meditation, completely resolves this dilemma. Both the implications and explanatory power of non-dualism are vast, and would require at least another book to even scratch the surface.
My first reaction is to say that this sounds like woo. At the very least, it uses familiar words in an unconventional way: how exactly do you inspect something from the "inside" vs. the "outside"?
At my most charitable, I think this is pointing to the same mystery of the phenomenology of consciousness that Sam Harris often discusses. I'm ok with there being mysteries in the universe. Uncertainty can arouse curiosity without precipitating a crisis. However, if you're not going to at least point in the direction of another resource that attempts to tackle the topic, it's probably worth scaling back on the promises you make instead of just intimating that they are "vast."