Personal note: the author, Steven Koonin, and I overlapped at Caltech. We were both undergrad physics majors. He was a year ahead of me… and I don't remember him at all. Our career paths diverged, to put it mildly.
He went on to become a well-known researcher, on the faculty and in the administration at Caltech. He was Undersecretary of Science in President Obama's Department of Energy. He was BP's Chief Scientist for a time. He's currently at NYU.
I did not do anything comparable.
So he's not some wacky crank peddling fake science. But he's unhappy and disappointed with the state of climate science today, especially as it pertains to influencing public policy. He distinguishes lowercase-s science from "The Science": many things claimed to be Settled Science, are—well, see the title—not settled at all, and may be off. Which wouldn't be unusual for science, of course. But (unfortunately) there are trillions of dollars and billions of lives at stake. A lot less was riding on the theory of phlogiston or the luminiferous ether.
Like all good Caltech grads, Koonin is a Feynman fanboy. And he pointedly quotes Feynman's famous 1974 commencement address on "Cargo Cult Science". His implication is pretty clear: there's way too much cargo-cultism in today's Science.
(Okay, one more personal note: Graduating in 1973, I missed Feynman's address by one year. You know who our commencement speaker was? Harold Brown. He was Caltech President at the time. And he was—sorry—so boring.)
To be clear, Koonin is not a "denialist": there's no question that the Earth is warming up, and there's no question that human activity, specifically greenhouse gas emission, has something to do with that. But much else is (heh) up in the air. It is, for example, not the fact that hurricanes have gotten worse. Sea level rise will almost certainly be manageable. Neither existing climate models nor data are solid enough to predict the likely future course of the climate, let alone act as guides to optimal policies.
And (probably worst) the media, government figures, and (even) some scientists who should know better routinely predict doom unless "something is done" right now. (Greta Thunberg has a good excuse: she's a kid. John Holdren, what's your excuse?)
The book's prose is clear, full of personal anecdotes. At times Koonin's frustration shows a little bit. For example, he once proposed a "Red Team/Blue Team" exercise, where an independent group of scientists (the Red Team) would subject a proposed document (written by the Blue Team) to a no-holds-barred critique, highlighting uncertainties, dubious analysis, unwarranted conclusions. The Blue team would defend as best it could, either solidifying its positions, or backing them off.
Good idea! Except it was considered to be wolfsbane by many. To the extent that legislation was proposed in the U. S. Senate to forbid federal funding for any activity that might "challenge the scientific consensus on climate change". And as a local note: both my state's current senators, Shaheen and Hassan, were co-sponsors.
You gotta ask: what are they afraid of?