It's written by someone that does airliner crash investigations. His central point is that "human error" as a term functions to redirect blame away from the people who establish systems and procedures. It blames the last domino vs the people who stacked them.
It's a quick breezy read, and you'll get the main points within the first 30 min or so of reading. I've found it useful for getting these ideas across to people though, especially more generic business types where "no blame post mortem" strikes them as some care bear nonsense rather than being an absolutely essential tool to reduce future incidents.