The volume collects talks given across decades, with later commentary, plus a biographical section generous in admiration. The idea tying them together is that nobody decides well with the tools of a single discipline, and that it pays to keep a handful of models from several.
What I took from it
The talk on misjudgement, the last one, which justifies the book. It is a list of tendencies that lead people astray, and one of them I use in every process mapping engagement: before proposing a change, find out who benefits from things staying as they are. An absurd process is almost never the product of stupidity; it is somebody's rational response to how they are measured or rewarded. Change the procedure without touching that and the process returns to its old shape within weeks.
The second is inverting the problem: instead of asking how to make this go well, ask what would guarantee it goes badly, and avoid that. It is easier to answer and the answers are more concrete.
The third is the circle of competence, which in a one-person business is a commercial decision rather than a virtue: saying that something is not my field is the only way the things that are stay sound. Turning work down for that reason costs money and is what prevents the work that goes wrong.
What I left out
Quite a lot, and it is worth being plain: the talks repeat each other because they were delivered separately, so you read the same argument three times. The edition is a devotional object, with more reverence than editing, and the biographical part is surplus. The investment advice does not transfer to anyone who is not managing other people's capital. That final talk has circulated on its own for years and can be read without buying the book.