[Alma Here. I’m away from the internet, so please be patient if your comment gets into moderation or I don’t answer. One of the other mods will free your comment from limbo (or purgatory, if it was naughty).]
Some writers, or at least the names assigned by publishers to a series, don’t end. If you have any question, look at the shelf of westerns at your local bookstore, and if you get to # 400 with the same author and character, you can be pretty certain you’ve found the Eternal Series. In other cases, the publisher says, “No, you have to keep going, because these are too popular to stop now!” You’ve encountered those, I’m sure, where the reader can tell that the writer dreams of killing off the protagonist just to be free of him or her. And there are the series that stop abruptly, leaving reader and characters hanging because the publisher decided that the series wasn’t producing. For indie writers, or those with more flexible publishers, we have to decide for ourselves. It can be a little difficult.
I am wrapping up two series this year, three if you include the Powers trilogy. I’ll look at the reasons in reverse order.
[cue Andrea Bocelli and Sarah Brightman “Time to say Good-By”]
The Powers: This was always meant to be three books. Come the third book, the series ends, because the main character has reached the end of what he can do, and because the alt-history aspect draws back into synch with our chronology, sort of. The story ends, and the series ends, all plot strings tied up, no muss, no fuss. Readers curious about the next events in that world can jump to Promises and Powers or Double Edged Wish (C.a.D four and three respectively) to pick up what happens next.
The Colplatschki Chronicles: This series will conclude with the release of the prequel in early August of this year, the first book in series chronological order. In terms of time, this is a messy batch of books, with events scattered across several hundred years and two continents on ColPlatXI. Part of the problem was that the series was not supposed to be a series, but one book. One book became four. Then the world proved so intriguing, and my Muse so demanding, that it ended up with eleven books, of which ten will be published. Since they were not written in series chronological order, finding an end point was a trick.
Reader demand provided the answer, as sales of the last two books were very low. Too many books, too many stand-alone stories, and series fatigue have combined to encourage me to end the series. I will publish the story of the Great Fires and the founding of Vindobona and Peilovna. That ends things on an up note, and provides a start-point for new readers who want to go in chronological order.
The “not intended to be a series” series may be the hardest to wrap up neatly. All the books share a world and a culture, but in some cases little else. If I were to go back and re-write the set as a “real” series, I would play up the importance of Sarmas and the DeSarm family, making that the linking thread connecting all the books.
A Cat Among Dragons: This was the hardest for me as a writer to bring to a conclusion. Rada was my first major character, she was my vent in grad school and I’ll miss her and Joschka keenly. However, the series needed to wrap up. I’d planned on ending it with the end of her life, but realized that readers were not going to like that. The reading numbers had been declining with each book since A Cat at Bay, because the story has gotten darker. It’s not the fun romp and world building that it once was. Hopeful endings and survival are not enough—my readers wanted a happy ending. So even though I have material for at least two more books, plus the one coming out this year, I’m ending things on a very up note.
However, that also meant that I had to gut and heavily rewrite the last book, because otherwise a major plot thread—OK, plot chain with three-inch-links—would be left flapping in the wind, thunking people on the head. Two chapters got cut out, three more added, and other chapters seriously pruned or trimmed. As it is, I may go in and remove another chunk to make the end even lighter.
(Added three days later: I did lop off 10,000 words or so. It had some really neat scenes and a cool setting, but the key event no longer made sense, and the end got far too maudlin for how the characters have developed. And that plot thread that I tied off earlier? Made the climax of the chapter moot to the point of possibly inducing book-walling. Not a good way to end the series.)
When do you end a series? When the story ends, at least for your readers. You, the author, may want to keep things going, but unless your publisher is demanding that you keep writing that world/character OR ELSE, eventually readers are going to get tired and lose interest. Ideally, you stop before that point, and leave them happy but wanting a little more. When your protagonist becomes a demigod is probably time to stop. When your protagonist is smiling from the porch of the Old Characters’ Home at his g-g-g-g-great grandchildren is time to stop (unless you are R. A. Heinlein). Before you get sick of the character is a great time to stop.
Tie off your major plot threads, send your characters off to a Pretty Happily Ever After as the Bad Guy hisses, “Curses, foiled again!”, and type
Then release your next book.