Every now and then I get an email that says something along the lines of “I just picked up your book, [insert title of eighth or ninth book in series], and loved it so much I went back and got all the other ones in the series.”
I love these emails, because they tell me I’m accomplishing one of my goals: to make sure each book stands on its own well enough to provide a satisfying read and potentially draw people into the rest of the series. These emails are a great reassurance to me. My instincts were right, and paying attention to this sort of thing while writing an open-ended, ongoing series really is important.
Making sure each book stands alone well enough to tell a complete and satisfying story is important to me, not just for the sake of aesthetics, but because every book might be some readers’ first encounters with my writing. Some readers put out the effort to make sure they read a series in order. Some don’t. I don’t — generally, I’ll read whatever’s available, whether it’s part of a series, first or last book in a series, or whatever. (The first Bujold book I read was Mirror Dance, because it had just won the Hugo Award. Not only is this book set in the middle of the series, it’s in the middle of a three-book story arc. And I still loved it.)
This doesn’t mean I can’t have an ongoing storyline, and that the characters have to remain static. On the contrary, I think one of the attractions of a series is watching characters grow and develop. What I don’t do is try to explain everything that’s happened in the entire series in each new book. In a sense, I want to treat each book like the first book: what does the reader have to know about these people to understand the story I’m telling right now. Any backstory I provide is brief and topical. I don’t really think of it as backstory, but as character description, along with clothing and demeanor. This character wears a leather jacket and has a resident Victorian ghost (because of what happened in book #6, but the reader doesn’t need to know that much detail to understand the story right now).
A couple of anecdotes doesn’t make for a hard and fast rule about how to write a series, but my own experience is that some people will read the later books in a series first. Maybe they got book #8 as a gift, maybe it was the only book available. But each book I write in the series, I have to ask: How will this read to someone encountering the series for the first time? That thought has served me well, I think.