George "Slim" Lewis was an animal trainer in the depression-era USA. He rode the rails from circus to circus, handling elephants. He specialized in unruly elephants. Thus, this book has a "thriller" aspect to it. You're reading along and every so often, someone gets swatted across a room. Or gored by tusks. Or crushed against a wall. Or sat on--sat on really, really hard. This book reminds you that elephants are not always nice, and that they are tremendous.
It's a tough book to read if you like animals. Back in those days, it was accepted practice to use an elephant hook. (I guess this is the same thing as an ankus.) It's difficult to read a narrated description of giving an elephant a shallow cut that will take days to heal. This man--he feels affection for elephants, he just learned that cutting them was a way to get their attention & respect in a hurry. He sticks by elephants when various zookeepers and entertainment industry promoters are ready to kill and/or abandon them. Elephants had it rough in this country.
There are stories about elephants, about circus life. I learned that "The Greatest Show on Earth" earned its title--at least it had an order of magnitude more elephants than most circuses did. There were also glimpses of life at some of the smaller circuses, and some of the strange politics around city zoos.