I wasn't sure what to expect when I picked up Death in the City of Light -- it looked a lot like The Devil in the White City, even with a similar title, so I was hoping it was another example of creative historical nonfiction.
The book does do an excellent job of weaving a very readable story of the serial killer of Nazi-occupied Paris, but I'd say it isn't quite as good as Erik Larson's work. It is, however, compulsively readable. I think the main difference seems to be that there is less dialogue in this than The Devil in the White City, which does of course make a history book feel much more like a novel, but also requires the author to be able to pin down documentation of actual things the real-life characters said.
One thing that I really like about Death in the City of Light is how King starts off with a prologue that tells about the gruesome discovery of the killer's victims, and then starts the story from the beginning in the first chapter: He describes the killer's childhood and education, making sure of course to include indications from friends and family that the guy was a little bit off, even as a kid. From there he starts talking about early indications of what Periot was up to -- patients and other people connected to him who disappeared, and that kind of thing.
The way the story is told, it definitely builds the suspense and keeps you reading!