I liked that it was a refreshingly rational and non-religious view on spirituality and meditation. I also liked that the book asked a lot of deep and interesting questions about the nature of consciousness and the mind and reviewed a lot of interesting scientific studies that showed very weird results about how our brains work (split brain, binocular vision, etc.). It's now pretty clear to me that the mind is not this one massive structure but that it can be divided and work independently in pieces, and we still know so little about it.
I didn't like the amount of time the author spent going into the intricacies of the failures of certain viewpoints and how certain authors are charlatans; I got the point quickly enough and thought that some of those sections dragged on a bit. I also didn't find the book to be too practical in terms of changing anything about how I live. My biggest takeaway and new idea (for me) was the separateness of self from consciousness. I still don't have a full understanding of what the author meant by this and how exactly one experiences it in the "right" kind of meditation, but at least now it's an idea I can think more about and explore.