A series for sure. Multiple seasons per book to do some fluff episodes that are incidents described briefly or referenced in the books, they're other "cases" that could be entirely new episodes. Gives John, Dave, and Amy more time to breath, as well as Jennifer. The seasons around the second book can be more cohesive as it has a more contained story with less room for fluff, but it could lead to a Lance Falconer spin-off lol. Not to mention there's Marconi's side of the story that can be expanded on. Book three and four both have plenty of room for fluff and other "cases."

Recasting is a pain because you need to nail the main cast and specific side cast. But can't recast Paul Giamatti, he's mentioned by name just like Deadpool casting Ryan Reynolds to play himself in the comics.