It's by Steven Pinker, acclaimed Harvard smart guy. I'm a fan, and his books get an automatic buy from me.
This one is on a huge topic, see the title: rationality. He mentions that it's based out of a course he gave for Harvard undergrads. In fact, at a number of points where Pinker makes some quip in the middle of a chapter, I found myself thinking: that probably got a few chuckles in the lecture hall.
What is rationality? For Pinker, it's a bundle of methods that are effective in moving us toward our worthy goals, most notably truth, progress, and prosperity. It's avoiding fallacies and biases. (There are a lot of those, and for your convenience, there's a separate index of them, about four pages worth.) But it's also avoiding silly (but common) mistakes; there's a long discussion of the so-called Monty Hall Problem, where a lot of Very Smart People got caught not thinking things through.
A lot of different topics are breezed through: basic logic; von Neumann's "choice theory" axioms; game theory; multiple regression; Bayes' Theorem; causation vs. correlation; statistical significance; … well, you get the idea. It's a real Cook's tour.
Simply by coincidence, I read this concurrently with another book, Escaping Paternalism by Mario J. Rizzo and Glen Whitman, that covered a lot of similar ground from a much different angle. A report will be forthcoming on that someday. And (for some reason) I seem to have been reading a lot of others in this ballpark in the past few years: The WEIRDest People in the World; Consciousness Explained; The Scout Mindset; Priceless; The Hidden Half; The Mind Club; The Origins of Virtue; Science Fictions; How to Think; and of course the biggie: Daniel Kahnemann's Thinking Fast and Slow, way back when.
So there's (kind of) the bad news: there wasn't a lot new, at least for me, in Pinker's book. And the last couple chapters break off from the science and move toward sermonizing, with a hefty dose of one-sided political animosity. Hey, I didn't like Trump either, but Pinker almost made me want to defend him.
And I was somewhat disappointed that Robert Nozick, another smart guy who was also at Harvard, didn't get a reference. He wrote a whole book titled The Nature of Rationality back in 1993. (Guilty confession: It's on my bookshelf, where it's been sitting unread for about 28 years.)
And kind of a wince-inducing assertion at the beginning of Chapter Ten, labeling the idea that Covid-19 "was a bioweapon engineered in a Chinese lab" as one of the "cockamamie conspiracy theories" surrounding the disease. To be fair, this is listed among a number of other conspiracy theories that really are cockamamie. And I don't think Covid-19 was intentionally designed and released as a "bioweapon". But I don't think the "lab leak" theory is even close to cockamamie, and a coverup conspiracy isn't unlikely at all.