A strange book. Calder provides 101 capsule biographies, which are in general fairly interesting.
However, it lacks any focus for the general reader. This is because it seems to be primarily just people he was interested in researching. This comes through in the large number of his own ancestors and people that he knew included. I can understand that he may be interested in these people, but that hardly makes them "essential lives" for the rest of us (that's his subtitle, by the way).
It also, bizarrely, includes a few mythological figures. Again, these are generally interesting histories. But they don't really fit in.
Calder also uses a number of the biographies merely as a starting point for his musings on related topics, sometimes hardly mentioning the person that the article is about.
Overall, an okay book with a lot of interesting biographies, but unsatidfying due to the lack of a real unifying theme (at least, to the world at large).