Executive summary: a big, deep, dense book that I almost certainly didn't spend enough time on to appreciate fully. My excuse: I got it from the Portsmouth Public Library, and only allowed myself two weeks to read it. In an ideal world, I'd probably have to spend much more time working through it. This report will be unfocused and choppy, apologies in advance.
It's by David Deutsch, a well-known physicist, and I kind of expected the book would be about (y'know) physics. Well, there is a lot of physics, but there's even more philosophy and speculation. And additional topics, like AI, government, and the nature of beauty. He never says "Did I just blow your mind, reader?" But he could have.
Among the things I did not expect: a long chapter with a scripted discussion about knowledge between Socrates, the Greek god Hermes, with a late appearance by the flawed scribe Plato.
Back in my University days, I studied (superficially) the philosophy of science: Kuhn, Popper, Lakatos, Feyerabend, et. al. I really wish I'd had this book then.
Deutsch is a fan of the Enlightenment (properly understood). In that, he's the physics-side version of Deirdre McCloskey, observing that the new Enlightened attitude toward science (specifically) and knowledge and creativity (generally) has opened up an unbounded possible future for humanity. (Worried that we'll run out of calcium, or something? Pshaw! We'll figure out how to transmute the vast quantities of intergalactic hydrogen eventually into whatever we want.)
He's a fan of the quantum multiverse, and his explication is (as near as I can tell) unique. He's scornful of the "shut up and calculate" Copenhagen-interpretation folks. (Although, admittedly, they get the right answers.)
He's also highly critical of neo-Malthusians and their concepts of "sustainability" (e.g., Jared Diamond). In my case, he's pushing on an unlocked door.
But he's not always pushing on an unlocked door. I have (in the past) expressed worries about the finite intellectual powers of humans setting an impenetrable ceiling on knowledge and progress. Deutsch is the only author I've seen who deals with this straightforwardly, and he debunks my notion pretty convincingly. I will re-evaluate my position! And not be so glib about it in the future.