The God of the Hive is the tenth Mary Russell-Sherlock Holmes mystery, and if you haven't read them stop whatever you're doing and go buy The Beekeeper's Apprentice (the first in the series) right now. This is the series I usually recommend when friends ask me for some interesting light reading, and I've converted quite a few people into fans.
The God of the Hive is the second part of the story that began in The Language of Bees, and ended in a cliffhanger. Personally, I prefer a single story to be contained within a single book in the mystery genre, although The Language of Bees and The God of the Hive do have two separate villains, so I'll let that point go. But they are not, strictly speaking, standalone novels. And this far along in the series, I guess they don't have to be.
I enjoy the Mary Russell books for several reasons: the edgy characters, the intelligent dialogue, the locations, the humor, and the fact that they're set in my absolutely favorite historical period, the "long weekend" between World War I and World War II. The pace is energetic, and given the age of some of the characters, they must be quite exhausted. King has succeeded in making me more interested in Sherlock Holmes than Arthur Conan Doyle ever did, which is saying something (probably something heretical from a Holmsian purist's viewpoint).
To review the plot would be to introduce spoilers (OK, I'm lazy, and book reviews that contain book synopses bore me), so let me just recommend the whole series to you and be done with it. It's elevated mystery writing in the tradition of Dorothy L. Sayers, and consistently enjoyable.