Bone Crossed picks up right where Iron Kissed left off, literally at the same scene. Mercy has chose Adam, but the emotional injuries from her attack haven't quite healed. Her mom shows up, and right around then Stefan, the Mystery Machine driving Italian vampire who's friends with Mercy, appears in her living room, pretty much dead, as in second dead, not just vampire dead. This is the start of what looks like the vampires starting a war against Mercy. That night, a relative of her attacker, now dead and torn to bits, takes revenge on Mercy by graffitiing things like 'liar' and 'whore' on her shop. Zee discovers a set of crossbones painted on the door that his glamor can't cover. On checking the security cameras, they discover that it was a vampire who painted them, and eventually find out that it's a curse.
Offered a way out of town for a while, Mercy leaves with Stefan to help her old college acquaintance in another city deal with a ghost problem. The very first night she encounters the vampire other vampires are afraid of, and, after making the ghost problem even worse, to the point that the family has to leave their house, she flees and returns with Stefan.
The fight with the vampires is resolved, and so is the ghost problem. There is a bit more about pack magic (werewolves), as well as vampire and walker magic, but a lot of it felt like it came up in response to the plot rather than being a part of the plot.
I enjoyed reading Bone Crossed, though not nearly as much as I enjoyed the other three. The story was okay, but it felt rushed. The editing wasn't as clean, and the story just didn't have the same believability as the other three. I think it was partly, again, because of that feeling of convenient magic to fix or respond to the plot. I liked learning more about the walkers, and I felt like there could be a lot there, but it wasn't very convincing. Mercy wasn't nearly as interesting a narrator in this one, and it was the pace and quality of her narration even more than the content of what she said.
I really liked this series, and I love the ideas behind the characters. Still, part of me hopes Briggs will leave it be, as excited as I was to find a fourth book. Unless she improves the quality of the stories, I'd like to remember this series as books I through III.