A brief overview of the recent revolution in soccer (sorry, football) analytics brought about by the expected goals (xG) statistic. This short book could have been a long essay — ideas and even specific examples are repeated — and the author routinely labors to explain what is a very simple quantitative idea. But the author's first-hand knowledge of the sports analytics and sports betting industries add interesting and useful context, and in the end I got what I needed from this book and more.