In one sentence.** It is about hiring, and about the uncomfortable fact that most organisations make their most expensive decisions using a process nobody designed.
Anyone responsible for who gets hired — the person running the process, not just sitting in one interview of it.
Hiring is the highest-stakes repeated decision most organisations make. A good hire compounds for years; a bad one costs money, morale, and usually somebody's confidence. And yet the process is typically a collection of habits: a job advert copied from the last one, interviews shaped by whoever happens to be free, and a final discussion where the loudest opinion wins.
The book's argument is that hiring is not one decision but a chain of them, each one quietly constraining the next. The most consequential are made long before anyone is interviewed — what the role is actually for, and what standard you are hiring to. Get those wrong and no amount of careful interviewing recovers it: you will run a rigorous process to reach a decision that was already distorted.
Write down what you are looking for, and what evidence would count, before you meet anybody. It takes about an hour, almost nobody does it, and it is the difference between a group of people comparing evidence and a group of people comparing impressions.
The book is also candid about failure. The author has hired roughly 200 people and writes openly about the ones he got wrong — which is what makes the advice worth reading, because most hiring books only describe the successes.