Being a member of RWA of many years standing, I get Romance Writers Report, a magazine every month with articles by various authors as well as what's going on in the business. This month there was a story that at first I didn't see as about my own books-- 'What I wish I'd known about writing a series before I started mine' by Janet Tronstad who wrote a very long standing series called Dry Creek.
I have never read the books. Looking at them on Amazon, it appears they are of the sweet romance type which isn't really my choice for reading, but they look well done and well... sweet. She now has 24 of them which means she is successful in attracting readers.
She said when she began she didn't know she was writing a series. That led her to not keeping all the details straight and ending up with readers letting her know. The readers of her books are loyal and pay attention to the details. Given she's keeping all her stories in one town in eastern Montana, a fictional town, she saw that she had to recognize some key expectations and meet them. I won't go further with her article but what reading it did for me was remind me of some of my own problems along the same lines.
Strictly speaking I had never seen myself as writing a series. But I have written a lot of books set in Portland, Oregon. I have written a lot of books that have similar characters and where a secondary character in one has led to a hero or heroine in another. I've had an advantage over Ms. Tronstad-- mine weren't published until I decided to put them all out. That meant I could clean up any messy little contradictions.
The first thing I did, when I decided I would put my contemporaries out as eBooks, was to look at the probable dates of each story. The ones that came first had to fit with those that followed for aging, relationships, etc.
In one book I had intended to use a secondary character who I already knew had been the hero of his own story. The more I looked at how complicated that would be, the more I decided it wouldn't work. I then renamed that secondary character and ended the problem.
Five of my books seem like a series, but they don't have that name. Desert Inferno is the only one of the five not set in Portland. It though connects with the others because of one family and a secondary character who ends up the hero of Bannister's Way. There were two years between which isn't too complicated, and it helped that the stories were not set in the same city.
One of those secondary characters in Bannister's Way was the hero of an earlier book, chronologically, Evening Star. As I worked through the logistics of that one with the age of a secondary character in Moon Dust who was the heroine of Second Chance, my mind nearly went blank.
When I wrote them, I liked the characters and wanted a love story using them, but I hadn't thought of them chronologically. When I did, it took some head scratching to see how that worked. Evening Star and Moon Dust both had to come first and Moon Dust by eight years. Evening Star I leave more vague other than it came well before Bannister's Way. Getting confused yet?
None of these books require reading the others, but in a way they are a series. I won't complicate this article more by mentioning that Hidden Pearl and Her Dark Angel are likewise one following the other, set in Portland, but none of the characters were in the other five which was done mostly to avoid having my head explode as well as understanding that big cities don't require everybody knowing each other (an aspect that wasn't true with the Dry Creek books).
With three historical novels set to come out next year which do follow one family through three different love stories, my problem was somewhat easier. There were two years between the first and second with over ten years before the third. All I had to do then was remember which secondary characters I might enjoy using as well as keep track of ages and the political climate of that time.
When I do a book connected to another, or really any story, I do keep notes. Before the explosion of software advances, I read it should be note cards for each character, but that didn't actually work for me as I tended to misplace or forget to look at them. What I do is write down the characters on a sheet of paper. I keep track of their ages and relationships to each other. This requires at least birth years and sometimes dates as well as arrows that connect one or another. Frankly I tend to feel I know these people as personal friends; so a lot of what they are like is just in my head. It's the little gritty details-- like eye color-- that can foul me up.
Finally I write again on a sheet of paper what was going on politically and historically during the years of a particular story. When I edited and expanded Luck of the Draw, having lived through that period (1974), I still needed a reminder for what music was popular. Love the internet.
Some of my characters have no interest in the politics of their time; but if say in the settling of Oregon, they cared about statehood, it's important to understand who wanted it and who did not. I use my list of dates and events as well as books with markers where there are important passages I might want to reread. My system isn't modern but it works-- when I don't forget to look at it.
Programs, which have been recommended to me as helpful, include PageFour (free), WriteWayPro and Scrivener. I honestly think I'd have to take a class to learn to use any of them as techie stuff is not my thing; but maybe someday I'll take the time to figure it all out. PageFour sits on my desktop reminding me I should do that. If I do, I'll likely realize I should have been using one of them all along. I am that way.