What sort of characters do you prefer in series novels?
I'm thinking specifically about series novels--each subsequent book is a self-contained story, although there may be subplots that extend over several books. That's how I'm defining "main plots" and "subplots," too: The main plot starts and ends in that particular book, and matches the genre where the book is categorized. The subplot might start and end in a single book or it might not; it might also be a second genre such as romance or family drama.
The first option, the single recurring character, is pretty much the "Lew Archer" method. Archer a customer hires Archer for a job, Archer does the job. No wives, no ailing father, no shadowy mastermind pulling strings behind the scenes.
The second option is more like Starsky and Hutch. The protagonist(s) have a couple of pals who help them solve their crime, or whatever, and they appear in pretty much every story. Although how Huggy Bear managed to reach the end of the first season without a bullet in the head is beyond me. "What are we doing tonight? Nothin'. Honest, Huggy, we don't have a thing going on tonight. Nope. Not a... Well, okay, I'll trust you just one more time."
The third option is similar to Sue Grafton's alphabet books, where Kinsey Milhone has a new mystery to solve every book, but there's a recurring cast of characters playing out a found-family drama. The "S" book started a romance, and that's when I checked out.
Option (what are we up to?) four is similar to the X-Files. Everyone is tangled up in everyone else's problems, and the plot engine requires the characters to seek out new characters and they're problems.
I just went back and numbered them all. Option five is pretty much Star Trek or Criminal Minds: Lots of recurring characters, lots of new ones.
Option six is a sitcom or prime time soap. The Dresden Files has become more like option six as the books have gone by--most of the characters, heroes and villains, have appeared in previous books.
What do you like?