Bonecrossed has Mercy Thompson, sometimes-mechanic sometimes-coyote, contacted by an acquaintance (Mercy wouldn't call her a friend) who has a rich husband as well as deaf child. Apparently, there's a ghost haunting her home and she wants to see if Mercy can do something about it. Mercy doesn't think this is a big deal because ghosts are mostly harmless in the Mercyverse. They're capable of moving objects around and making the occasional spooky noise but can't actually harm someone with their powers.
Unfortunately, the situation is a lot darker than she imagined. Her friend is living as a slave in the household, seemingly unaware of the missing time she experienced. Her husband is also completely unaware of what's going on inside his home. Only the child has any real sense of the danger they're in and he can't communicate well. This immediately takes Mercy out of her comfort zone as she's not a talented investigator and not used to working outside of her home. Alone in a house of untrustworthy people, away from her allies, she's forced to improvise a solution.
Things go from bad to worse and soon Mercy finds herself facing the most powerful vampire she's ever encountered who is able to stand sunlight and possesses a menagerie of supernatural slaves. Mercy, as always, ends up losing control of her situation and having to think her way out. I wasn't as big a fan of this novel as I was the previous ones. The villain didn't really wow me as Jim Blackwood didn't have nearly as much personality as characters like Marscilla or Stefan. The fact he was abusing Mercy's friend Amber is also dealt with way too casually. Indeed, Amber seemed like a throwaway character and I didn't like that one bit.
I am pleased the book nicely resolves the love triangle with Adam and Samuel. Really, it was resolved in IRON KISSED but I think this book made it clear there's only going to be Adam from now on. Unfortunately, this book also begins the tradition of the needless drama where Mercy is hated on by Adam's pack because they're racist against coyotes joining. I also found it difficult to believe Adam wouldn't be there with her as soon as things got troublesome for her. Instead, the reasons for her being alone at the climax felt contrived. Still, we got the Walking StickTM out of it and I have come to love Mercy's signature weapon.
The tension in the story is considerable but this feels more like an expanded short story than an actual novel in the setting. Much of the appeal of Mercy Thompson comes from the series' extended cast of characters. Here, we're mostly stuck with a creepy family that Mercy has to uncover the secrets of. It's not a bad premise but I miss the vampire, fairy, and werewolf politics that make the rest of the series so great.
In conclusion, Bone Crossed is an okay novel but not one of my favorite of the series. The reasons for Mercy not having Adam or the pack were contrived and I felt she spent too much time among the new characters who were, ultimately, throw away and unlikely to be seen again.