As a recent (~last five years or so) fan of soccer beyond watching the US at the World Cup, and as someone who respects how insightful data analysis can help us see through what turns out to be weakly justified or even flatly erroneous received wisdom, this book should have been in my wheelhouse. And indeed, parts of it were. There are a lot of interesting points made here about a range of topics, like how, contra the complaints of supposedly beleaguered fans, England actually overperforms in international soccer relative to it's soccer history and demographics, how a common nativist argument (e.g., "there should be more English players in the Premier League") is misguided because it neglects how the collection of international stars who populate the EPL actually push England's EPL players to improve, and how the primary benefit of hosting a World Cup is not financial (as has become increasingly clear since they published just a couple years ago, hosting a World Cup or Olympics doesn't bring economic returns) but emotional (i.e., host countries, much more so than winning countries, tend to experience increased happiness after such events).
However, almost every chapter contains either a claim that is vastly overstated relative to the data that they have available to them, or contains a massive conceptual error. Overstating points may be slightly excusable, especially since their editors are probably forcing that kind of frame on a book meant for popular consumption rather than academic consideration, but I still don't find it completely excusable. What's unforgiveable, and what makes this book earn the lowest possible rating, is that the authors have a couple of grossly misused (because misunderstood) instances of trendy scientific ideas that makes it seem like they've only bothered learning about it from recent article in Wired, or skimming one of the books by the modern master of this kind of fluffy-pop-sci-writing weakness, Malcolm Gladwell.
Case in point: the second chapter is an extended argument for why soccer teams should maximize money spent on player salaries, and minimize money spent on transfer fees. That argument itself seems plausibly-supported. But they then try to figure out why one of their heroes of the chapter, Lyon, managed to come out of nowhere to win the French Ligue One for seven years through a policy of finding good players young and selling them while they still had value; basically they won because they were able to play the transfer market arbitrage game exceptionally well. The reason they give for their ability to do so well: the "wisdom of crowds", which they say Lyon had because instead of a single manager making personnel decisions, they had an entire five people get together to make those decisions. Anyone who has any knowledge of the theory of the wisdom of crowds knows that five experts sitting in a room is not a crowd! That's just a committee, an entity which sometimes works well by pooling ideas, and sometimes are even less effective than a single decision maker because focus is muddled. But they're not a crowd! The wisdom of crowds idea is that in *some* situations (guessing the weight of an ox at a fair is the classic example), with sufficiently diverse sets of people, the knowledge of large groups of people can get closer to the correct answer than the experts, because their collective errors in answering a question will tend to cancel each other out. It doesn't always work, especially in cases where later parts of the crowd can see what earlier parts of the crowd did, which can create an information cascade (since the later people intuit that the early folks were on to something, their own guesses can get skewed by whichever opinions randomly showed up first). (Side note: for authors who spend so much time talking about "knowledge networks" being the key that explains most of modern soccer, it's curious that they've apparently never considered another network phenomenon the concept of an information cascade, which is often the basis for the most obvious foolishness of the crowds results: market bubbles.) And it's almost certainly true that any real world application of using the opinion of actual crowds (i.e., the fan base) rather than modestly-sized committees to choose which players to sign will inevitably lead to signing big name, past-their-prime players for too much money. I have no problem believing that these five guys in Lyon were especially good at their job, using good Moneyball-ish principles to sign players at a time when other clubs were not, but there is nothing in what Lyon did that comes even close to seriously implementing wisdom from crowds, and any attempt to say otherwise is the result of rank amateurish thinking and research. While this error was the most egregious, there are similar conceptual errors sprinkled throughout this book that suggest that Kuper and Szymanski themselves need to broaden their own knowledge networks and read scholars and sources outside of their own narrow domains of interest (or at the very least, stop talking authoritatively about things they know almost nothing about).