Key Out of Time
Andre Norton
This is another of the Time Agent novels, that includes Ashe Gordon and Ross Murdock. In this one, they are on a distant planet and use the time machine to try to learn some of the history of the planet. When things go wrong, they get involved in that history.
I won't go into greater detail for fear of giving away the plot. This is a good book in an older style of Science Fiction, and it is much like the Science Fiction I cut my teeth on, 40 years ago. You must understand that this was not the most recent Science Fiction even then. It has a pretty good story, and Ashe and Ross are good characters that are familiar to those who have read books in the Time Agents series. I have only read two others, and I was not sure about one of them until I read this one.
Much of Norton's catalog can be gotten for free on Kindle, so there is plenty to read if you want to come to know one of the lesser, but still significant writers from the middle years of Science Fiction. She was not really on the cutting edge, but she had a good career as a writer.
This was a good read, especially at the price.