A truly excellent book. Spencer calls attention to three things we all SHOULD HAVE figured out for ourselves. And it is a book about the science, not at all about the leaked emails (which other books have handled very well).
First, Spencer makes a powerful case for the heretofore largely understated role of clouds. Second, his presentation of material on the feedbacks was outstanding. I had never seen the distinction between amplification of forcings, and true positive feedbacks (in the run-away sense), made. Thirdly, his notion that choosing the wrong (weaker) forcing element for a given warming can result in a large overestimation of sensitivity is clearly right. Every physicist or engineer KNOWS these things, but we may not THINK about them. Luckily we have Spencer to remind us that we do know them.
As for the PDO as a major driver, the evidence Spencer shows is very interesting and well-presented, and is clearly much much better that a CO2 explanation. (To just say it is a better explanation that CO2 would do it an injustice.) The book makes the point that there are indeed many strong sources of internal variability. The so-called "consensus" in concentrating on a flawed, politically popular view (man-made CO2), is certainly effectively impeding progress toward a more rational understanding of the scientific puzzle.
A second excellent book by Dr. Spencer - for the layman (or scientist!) who still thinks.