The biggest thing I learned about the Joker that I didn't already know was his (generally gentle) anti-authoritarianism. That's funny, because I checked this book out from my library two weeks ago, just before Michael Malone got shit-canned by the Nuggets, and one or two tidbits in here are Jokic butting heads with, or having some passive-aggressive anti-authoritarianism with, Malone.
Not a new thing, but a reinforcement and backing up of something I've known for some time? Jokic, beneath his jokes, is serious about basketball and serious about winning.
Kind of serious NBA fans who are a step above casuals with Jokic may learn a fair amount, but for those who know more, this won't be that revealing.
Also, the writing level? Dozens and dozens of two- and three-page chapters? More than one occasion of someone who's been referred to not just once, not just twice, but several times, 10 pages later being mentioned by full name as though they'd never appeared before. A mix of first-name usage and last-name usage on some references, too. In other words, the book is thin on overall content and also needed a better editor.
Not bad, but it's your typical modern 3-star sports book. And, it's not on my "biography" shelf because it's not really a biography.