Overall, this is just a poorly organized book that left me learning nothing and I feel deeply frustrated because I do agree with much of the author but they just did a terrible job of making their case.
The central thesis is that crowds of people are good and attempts to disrupt these crowds are bad. They take a look at something like the burning of Paris in the 1870s as a false idea of crowds and says the commune of Paris was a great project. They don't mention how the wide streets of Paris were designed by Haussman and Napoleon to make it easy for the army to march through it.
The author gaslights the reader multiple times. The fires in Paris were what convinced a writer of the mob mentality that can develop from crowds. The author then says this mentality has been disproven. But they do not provide this proof.
The author says that in a crowd a person is not a mindless node in a system but retain their individuality. Then they spent the rest of the book bouncing between saying crowds make you a mindless node or remain an individual depending on the specific point they're trying to make.
When I think of mob mentality from crowds, I think of the violence that comes from mobs like the French Revolution, the Cultural Revolution, or the Nazis. The author spends time talking about January 6th and Nazis and claims that these were not 'crowds' but some other sort of thing that... the author goes on and on but somehow conclude that the Nazi rallies were not valid crowds in a very specific way that they define so that crowds are always good.
Another issue with crowds are during large events when people can get trampled. The author looks at research for crowds in music events and says that a crowd is a collection of mindless nodes which move to prevent trampling. A bit later they acknowledge that sometimes people can suffocate at music events.
They complain about the forces that try to create space around crowds to prevent trampling and suffocation and other deaths from crowds while all the ideas they offer still implicitly admit that crowds are not these perfect collections of people.
Crowds can be great. It's great to listen to a band together, or just being in a city that feels alive. Yet when there are problems, crowds can also lead to problems. Crowds can turn into riots. Crowds can be led to political crises. Crowds can be violent or unorderly.
If the author had tried to thread a needle, to discuss the psychology of crowds, of mobs, of riots, and how they may happen and may all be different, that would be an interesting book. If they had given examples outside of their own narrow world, that would be interesting.
They never mention being in a crowd in a church and the spiritual benefits around that. They seem to ignore the way that guns in the US can create a different risk model for crowds. They seem to dismiss random acts of violence and terrorism and how those fears can affect both policy and individual psychology. When the Eagles won the super bowl we saw people climbing telephone poles and lighting fires and people were clearly goaded into it while they probably would not have done that in the day on their own.
By being single-minded on defending crowds, they show their lack of interest in actually understanding crowds or persuading others that crowds are good. They complain without understanding the policies being made or the opposition to the author. And so this work is just a guy who is salty and blames everyone else.