Genuinely useful in 1984; now mostly a museum of its own success.

My copy is the "New and Expanded" one, which in practice means the case studies have been swapped for newer case studies and the argument has not moved an inch since the Reagan administration. Expanded! That's not automatically damning. The six principles are real, and reciprocity and commitment-and-consistency in particular are as good a piece of applied psychology as the trade shelves have produced. But there is a difference between a book that discovers something and a book that has been photocopied into every marketing seminar on earth for forty years, and this is now emphatically the second thing.

Reading it now is a peculiar experience. Every anecdote arrives pre-worn. The Hare Krishna flower, the car dealership, the compliance professionals who are always, always described with a sort of admiring shudder: I had met all of it before I opened the book, secondhand, through people who had also met it secondhand.

What actually irritates me is the structure. Each chapter opens with a principle, illustrates it six times, then closes with a "how to say no" section that is invariably the thinnest part and reads as though an editor asked for it so the book would feel less like a manual for manipulators. It doesn't work. It is a manual for manipulators — a rather good one — and it would be a better and braver book if it said so on page one instead of apologising at the end of every chapter.

Five. Chapter 3 is worth an hour. After that you are reading advertisements for the earlier chapters.