On DetecToday we're discussing what makes a novel a P.I. novel and whether today's trend toward multi-viewpoint books with P.I.s in them falls within the P.I. genre, expands the P.I. genre, or falls outside the P.I. genre.
I can see connections from Hammett and Chandler's work to that of anyone writing P.I. novels today. I include the works of Lee Child and J.D. Rhoades, etc. when I say P.I. novels because the archetype is the same.
With my definition of genre as "works with the same archetypes", I don't see the P.I. genre as growing. There are changing trends within the genre—hence all the troubleshooter/salvage consultant/repo men—and these trends are necessary to keep it relevant. But the archetype and core stories are the same, so I say the genre is the same.
I think more is definitely expected of P.I. novels than the protag being a P.I. Novels with doctor protags are not by definition medical thrillers, for example.
A single viewpoint has worked well to mark P.I. novels because people expect to read about one character's actions. They expect to follow an investigation. Thrillers often water down the investigation aspect due to space concerns/covering multiple viewpoints. Too many viewpoints in a P.I. book and I start wondering when the P.I. will pick up on what's really going on. With one viewpoint, the P.I.'s perspective may not be what's really going on, but it's the only information I get. I have to believe what the P.I. believes until more information comes along, a good pacing device.
I don't automatically consider multi-viewpoint novels outside the P.I. genre, but with multiple viewpoints it's more difficult to give the P.I.'s investigation the focus it would have in a single-viewpoint novel, focus that normally marks the genre. If a novel does not sufficiently focus on an investigation by an independent, experienced protag—be it single- or multiple-viewpoint—it is not a P.I. novel.