This is a fabulous little book..., fabulous. Just 125 pages, it should be read by anyone interested in history or in meta-history.
The book has three parts. The sections on Mussolini and Stalin are based on the author's private conversations/interviews with them - and contain some remarkable material. The section on Mussolini is the best. The section on Hitler is not based on any first-hand familiarity, though Ludwig does describe one revealing anecdote when he saw Hitler "ambling" down a wide stairway into the lounge of the Kaiserhof in Berlin in 1931, twirling a ring of keys on a metal rod.
Ludwig, a German living in exile, was an anti-fascist and a liberal - and had a beautiful pen and an insightful eye. He saw himself as an observer of history (and great men) in the making, like Xenophon (whom he thus overrates) or Thucydides. And while he is not the latter, he does surpass the former.
Here is a transcript of his interview with Stalin:
http://www.marxists.org/reference/archive/stalin/works/1931/dec/13a.htm