As someone with a very similar background to Ma's (engineering background, entrepreneur funding a company while playing poker professionally, and heavily involved in sports analytics from a predictive standpoint) I found this book to be an an articulation and formalization of concepts that every successful gambler has honed and inherently understands and has a tough time explaining to the general population. By definition, gamblers have trained themselves to evaluate the EV of every situation and make the most +EV decision while remaining emotionally detached from the results. Successful gamblers also understand bankroll management and non-results oriented thinking. We're trained to learn from trial and error, to correct mistakes via feedback, but variance has an inherent way of throwing these feedback mechanisms off. The way to better decisions, as Ma says, is to understand the underlying mathematics, ask the right questions, and maintain discipline.
Perhaps the most glowing recommendation I can make about this book is via my own personal experience. For the past couple months I've had a conversation with my father, a trained engineer and a brilliant man, about poker and investing. Each time, I tried to make the case for non results oriented thinking. The first example, I brought up the fact that I was up a large amount playing poker in Vegas and ended up marginally up. His statement is that I should have quit while ahead while my argument was that as long as I had an advantage (I was +EV in the game) I should try to realize this advantage by playing as many hours as possible, because in the long run, I'd hit my hourly expectation. He argued while that was true, my time horizon in Vegas was 1 weekend. I tried, unsuccessfully to argue with him that my time horizon was every time I played poker going forward, assuming my underlying assumptions about my EV in the game was still correct.
Likewise, he owned a stock that he bought at 3.00 which went to 16.00. He didn't sell it and kept saying he should have sold it while I argued that the stock was either +EV to own (undervalued), or overvalued and he should sell. If he thought it was undervalued, he should buy more, wagering a portion of his retirement account (his bankroll) proportionate to his edge. The fundamental mistake he made was overbetting on that stock and his inability to separate himself emotionally from the results given his limited time horizon (retirement looming).
Ma's text does a great job of explaining these concepts to someone who hasn't honed these thought processes, someone with no gambling or statistical background.
I think the book could have used a little bit more detail and explanation of some of the technical concepts. While Ma does a great job of simplifying the concepts, he doesn't provide very in depth technical explanation (he may have lost his audience). For example, more specifics on some of the metrics the 49ers used, more in depth explanation of the Kelly criterion, expected growth, how to manage an investment bankroll in relation to Kelly.
Either way, it's a book that I think everyone should read and those familiar with the concepts will gain something from it.