I haven't read anything by him. For what it's worth, the book has sixteen five-star reviews on Amazon, and nothing else. I would be a little wary because he's done some cowriting in other books with Sandra Ingermann, who has struck me as rather fluffy. I would probably also consider Cowan's work to be neoshamanism, just given the summaries and such that I've read. Still, that can be useful. His work is on my to-read list, so eventually I'll get around to reviewing it, but that's what I can say for now.