The third and what the author says is the final installment in the John Wayne Cleaver trilogy. The first two books: I Am Not a Serial Killer and Mr. Monster were both great books. I Don't Want to Kill You makes the trilogy fantastic.
I don't want to say very much about the plot of the book because I don't want to spoil anything about the previous two. In my review of Mr. Monster I described the unique character of John Cleaver, so I'll refer you there if you want to get an idea of what he's all about. I enjoyed reading the first book a lot, but for awhile after reading it, I remained uncertain about how I felt about a surprising and jarring turn the book took midway through it. I enjoyed Mr. Monster more I think because I was familiar with that aspect of the story and could enjoy it for the ride that I realized I was taking. With this last book, I really can't say enough about how great a series it was.
Hopefully Dan Wells has many stories like these yet to come.