The humor in this book was fun. Ritter is both dry and snarky. The book is not a funny book but it has funny moments. The humor comes from the characters and the situations. For example, Jackaby has an unfortunate tendency to be arrested on a regular basis as he's always getting involved in police investigations and they don't like it: 
 "That reminds me," he said, pausing. "There's a jar in my office marked 'Bail.' If you don't hear from me by tonight, just bring it down to the Mason street Station, would you? I'm usually in the first or second cell." 
 He also has his own way of expressing concern: 
 "Don't thank me. Just do your best not to die, would you? Oh, and one more thing Miss Rook. Promise me, if you do become a pigeon or a hedgehog or something, you won't get all stubborn about it." 
 Jackaby is an odd man and doesn't care in the slightest. He has few social graces, is given to oblique statements, is brusque, clever, and eccentric. He is a detective of the paranormal who goes through assistants at an alarming rate. His last one, Douglas, was turned into a duck and lives with him in a pond on the third floor of Jackaby's house. 
 Abigail has run away from home, she's in her late teens as best as I can tell, looking for adventure. Her first attempt was unsuccessful so now she's landed in the small New England town of New Fiddleham. She takes a job with Jackaby and they are immediately caught up in a murder mystery. 
 Abigail is smart, spunky, adventurous, and eager. She can be impulsive but her heart is good. Jackaby finds her useful but also gets impatient with her. The blurb compares him to Sherlock and they are both good at observation and picking up on subtle clues. Abigail quickly learns how to handle her employer and adapts to his other roommate, Jenny the ghost. Jenny and Douglas the duck are, pardon the expression, well fleshed and interesting characters. Then there's detective Charlie Cane who has an eye for Abigail and she for him. He works with them to try to solve the mystery and tries to run interference with the other police. 
 Ritter has an eye for detail and the mystery was well done. I did suspect who the villain was early on, it was obvious to me, but it took me much longer to identify what he was. Ritter makes good use of traditional beings from mythology and fairy tales. He also does an excellent job with characterization, making everybody complex and interesting. "Jackaby" is engaging, pleasing, and fun. It mixes whimsy, adventure, the paranormal, mystery, and a hint of romance for brew that's smooth and quenching.