I really like Parker's youtube content, and decided I should support him by buying his book! Unfortunately there is no kindle version available, and shipping of physical books doesn't work during CoVID, so I had to pirate it. Sorry Matt, though if you read this, I'd be more than happy to send you (or a charity) the cash!
Writing about math is a terribly difficult job. The vast majority of the population doesn't give a shit, and the people who do probably already know the things you're going to tell them. We're all starved for good math content! Humble Pi's target audience appears to be "people who liked math in high-school, and haven't touched it since. " It's got enough detail of the math problems to catch your attention, but not enough to actually help you understand what's really happening here. You won't learn any math here, but you'll probably learn about some things to wikipedia later. I liked a lot of the intuitive explanations of some of the described phenomena, but overall felt the book was lacking in substance.
If you follow Parker on youtube, this book doesn't have much to offer you, and his book persona doesn't come off as being as fun as his online one. I'd suggest giving this book a skip, but checking out his videos online instead.