Mr. Cook has added some science fiction to this fantasy series. Of course, the usual characters, not understanding the concept of science, understand the science as very advanced magic.
There's a reason why Garrett's still in the P.I. business after all these years -- he's not one to learn his lessons. Maybe that's why he lets himself get roped into being a bodygurard for Kip Prose, an obnoxious kid being threatened by creatures that can't be described.
According to the kid, the attackers aren't after him at all -- they're just trying to get to his frinds Lastyr and Noodiss. But before Garrett can get Kip to explain just who or what Lastyr and Noodis are, Kip is abducted, and the chase begins.
If you like Simon Green, Jim Butcher or even Rowling, Glen Cook has a good series in the same vein. Take a look online about the Glen Cook series and get the first book. You'll like it and is guaranteed to keep you interested in the following books.