I like reading series mysteries. Rex Stout, Ross Macdonald, Tony Hillerman, Sara Paretsky, and many other authors, even (God help me) Erle Stanley Gardner. Right now I’m re-reading the Brother Cadfael series by Ellis Peters. There’s something comforting about a series mystery. You know, more or less, what you’re getting into, but there are always fresh surprises.
I’d like to write a series. Or at the very least, I’d like to have the manuscript of a first novel in a series that I could pitch to an agent in the hope, however dim, that the agent would like it and sell it to a publisher.
I’ve self-published a couple of mysteries, While Caesar Sang of Hercules (historical) and Woven of Death and Starlight (YA fantasy, but also a whodunit). You can find them on Amazon if you spell my name right. In both cases, I tried to come up with a sequel, but my ideas for stories never caught fire. And I know why. In both of those books, the main character has a serious personal predicament that is emotional in character.
An emotion-laden problem is not a plot kernel that can be repeated. Only in soap opera can a character be run again and again through one emotional wringer after another.
In mystery series, the sleuth stands somewhat apart from the emotional turmoil of the case. Various authors handle this emotional distance in various ways. Lew Archer is almost a movie camera; he seldom reveals his feelings about anything. Archie Goodwin gets into emotional tangles, but those are with his boss, Nero Wolfe, not with the people he’s investigating. Brother Cadfael has active compassion for the people around him, but the emotional tangles of the stories are not his tangles. V. I. Warshawski does get tangled up in other characters’ emotions, but not in a way that’s healthy or even personal. She’s just a raw nerve.
Series sleuths do face personal physical danger, but that’s a different thing. It’s a convention of the genre, and in the end it’s not very interesting.
Right now I have an idea for a sleuth who I think could work very well in a series, if only I could see how to set it up. I don’t think I can make her a Brother Cadfael; she’s too cynical. She wouldn’t make a good Lew Archer; she has too much attitude. She wouldn’t make a good Warshawski; Warshawski is just tiring, and I don’t want to go there.
If I give her a personal emotional difficulty, she won’t be viable as a series sleuth. But if I don’t, I may not feel moved to write her into a book. The days when mysteries were just puzzles to be solved (as in Agatha Christie) are long gone. Readers crave a little soap opera.
Ellis Peters is fond of using star-crossed lovers. At the end, Brother Cadfael has somehow arranged it that the attractive, well-meaning young people can come together. That might work — but arranging for lovers’ stars to be crossed is a lot easier in a historical than in a modern setting.
I’m not sure what direction to go. I do like my sleuth, though. I think you’d like her too.
Jim Aikin's Oblong Blob 
You say this, but Jo Nesbo has his Harry Hole series and that guy has been selling books like crazy in a series that’s 13 books and counting.
I have no idea at all which of my statements you’re referring to when you say “this,” nor do I have the faintest clue how the series you refer to would contradict (in some unspecified way) what I said.
…Yeah, I was a little too quick on the draw there. My point was that detectives with inner turmoil can be incredibly successful, which you yourself pointed out.
I don’t think emotional turmoil is quite the same thing as an emotion-laden problem. Turmoil can drag on for one novel after another without ever being resolved. A problem requires a solution. And once it’s solved, it’s solved. It can’t be repeated in the next book. Emotional turmoil is just part of building a character. It can affect the plot — for instance, if the sleuth is traumatized by a long-ago incident involving guns, and in consequence refuses to carry a gun — but it doesn’t _drive_ the plot.
Yeah, you’re right. My reading comprehension is awful.
Either way, I’d love the idea of a new female detective series, especially if its of the noir or hardboiled variety. That (sub)genre has sort of been too much of a man’s game for a while.