The Men of Mystery are Rasputin, Gurdjieff, Helena Blavatsky, Nikola Tesla, Crowley, Dashwood, Geller, Nostradamus, and Mesmer. As you can see, they're not all men.
There's one chapter per featured 'man' of mystery running to 15 - 21 pages, apart from Anton Mesmer who receives over 50 pages. The story about Mesmer has selected facts and dialogue juxtaposed for continuity and doesn't read as accurate for that reason.
Mesmer sounds a remarkable person with fascinating ideas for curing people's health issues. I'm interested in finding out more about him, as is the case with almost all the people featured. The chapter on Nostradamus is fairly thin and I'd like to see more analysis on the interpretation of the verses he wrote, which at first reading feel like horoscopes i.e. vague enough to be open to many different points of view and biases.
Nevertheless, this is an enjoyable book and I would recommend it as a useful starting point for discovering the careers of these mysterious people.
Colin Wilson's introduction and chapters are informative, interesting and fun to read which is a big contrast from the others authors. The article on Madame Blavatsky is awful and the others not far behind. Recommended for Mr Wilson, but not the others.