Book Review: Ghostly Echoes

Ghostly Echoes is the third book in the Jackaby series. It covers the death of the resident ghost of 926 Augur Lane, Jenny Cavanaugh. She was murdered ten years ago, and her fiancé (a scientist involved with some suspicious
people) disappeared. She has hired Abigail and Jackaby to investigate her death. But when a similar crime happens, they realize Jenny's case is connected.
Because of the fact that this not only deals with the murder of a liked character, but also includes peeks into Jackaby's past and how he became the seer, this is the darkest book in the Jackaby series. But it also has plenty of humor, mainly in the bantor between Jackaby and Abigail. They feel like The Doctor and their companion from Doctor Who, if they had to take up the role of Holmes and Watson for a day. This also tackles a whole new part of the world building. This always had folklore involved, but now it includes mythology.
As good as this was, there were some problems. I feel like this book series needs more details; I can't see the character's faces all that well. Also, it is implied that Jackaby has feelings for Jenny, which I think needed much more foreshadowing. I only got close friend vibes from them in the first two books. And the side characters still needed some development; they were important parts in the book, but they didn't make much of an impact on me.
Overall, I think this was the best book in the series thus far, and sets up the events for the fourth (and final) book well.