This is a collection of six novellas with common central characters. They are stories of Dr. Erasmus Darwin, a real historical figure who was, according to the appendix, quite an interesting person in real life. However, the exploits in these stories are fictional. Each story presents a mysterious situation which appears to be some sort of supernatural manifestation, and presents Dr. Darwin as a very Holmesian master of observation and deduction, who then has some adventures in the course of solving the mystery.
They're entertaining stories, well written with reasonably solid plots. The characters are reasonably engaging, but pretty much static. It was fun to read, but I don't take anything significant away. 8 out of 10.