Abigail Rook serves as our narrator and stand-in. She's fresh off the boat in New Fiddleham, having cut ties with her family to go adventuring in Eastern Europe. Things have not gone according to plan, unfortunately for her. She's hungry, homeless, and jobless. No one will give her a job. By chance, she spots a notice in the local post office directing her to R.F. Jackaby, who is looking for an assistant to help him with his work as a detective. When Abigal tracks the man down, she discovers that he's the man she met her first night in New Fiddleham. He told her she had a Ukrainian fairy living in her hat and a kobold eating the rust off her coat.
For the first third of the book, Ritter plays coy. It's impossible to say whether or not Jackaby is crazy or is actually telling the truth about the creatures and auras he sees. Abigail is willing to play along—at least until she meets the ghost that lives in Jackaby's house. Jackaby lives in a strange, lonely world. As far as he knows, he's the only Seer in the world. It's an uphill battle to try and convince people that ghosts, banshees, leprechauns, and other ghoulies and ghosties and long-legged beasties exist. Abigail is a swift convert to Jackaby's reality.
Jackaby and Abigail's first case involves the grisly murders at a local apartment complex. A journalist has been found with his chest ripped open and his blood missing. Local Detective Marlowe doggedly follows the police rule book while Jackaby and Abigail take a more circuitous route to figuring out what done it.
Jackaby has a lively humor to it. I was chuckling through most of it. (I kept running across passages that were so delightfully funny that I wanted to quote them all. I resisted because quoting that much would violate fair use.) Gender is a rich source of humor. As it's the late 1800s, women are often brushed aside with comments about their unsuitable temperament or general physical and emotional weakness. Jackaby himself makes some comments like this that get him punched in the nose by a furious Irish immigrant. Ritter's female characters turn the historical sexism on its head.
The only criticism I have of Jackaby is that it was too short.