Jackaby by William Ritter

Newly arrived in New Fiddleham, New England, 1892, and in need of a job, Abigail Rook meets R. F. Jackaby, an investigator of the unexplained with a keen eye for the extraordinary--including the ability to see supernatural beings. Abigail has a gift for noticing ordinary but important details, which makes her perfect for the position of Jackaby’s assistant. On her first day, Abigail finds herself in the midst of a thrilling case: A serial killer is on the loose. The police are convinced it’s an ordinary villain, but Jackaby is certain it’s a nonhuman creature, whose existence the police--with the exception of a handsome young detective named Charlie Cane--deny.

Doctor Who meets Sherlock in William Ritter’s debut novel, which features a detective of the paranormal as seen through the eyes of his adventurous and intelligent assistant in a tale brimming with cheeky humor and a dose of the macabre. (summary taken from Goodreads)