Substance. Peterson is the king of verbosity. Self help books with 12 guidelines don't need to be 400 pages.
An example.
The big thing people use when discussing Peterson is the following rule: "Set your house in perfect order before you criticize the world."
On the face of it, this is a thought provoking concept. The average reader may look at this and ask themselves, "do I really have the grounds to make criticism of society/someone else/etc when my life isn't in perfect order?" and proceed to put any criticism or critique on the back burner to improve their own life.
However, even the most cursory exploration of the idea shows that it's not thought provoking, it's thought terminating. Scrutiny of the rule and how it's applied shows that it's easy to abuse in order to shut down discussion or criticism. If I criticize your actions or behavior, for sake of example, you could respond with the rule to attempt to get me to stop criticizing you.
Its a lazy, dishonest method to deter critique or commentary.