Indie Author Snapshot: Number of Books in a Series

One of the questions I wanted to answer, when I pulled together my snapshot of indie fantasy authors, was whether there was a "sweet spot" in the number of books which should be included in the same series.

As most indie authors are aware, writing a series of books can be far more effective than writing standalone novels. A series makes it easy for fans of the first book to find the next book by the same author. Series drive read-through, which also makes advertising costs more effective: a single ad can promote an entire series of books, not just one.

Conversely, there's always the question of whether writing a lengthy series of books set in the same world or with the same characters will result in reader fatigue. Even if the next book is set in the same world - would it be better to include it as part of the original series, or might it not be better to begin a new, spin-off series? What is the optimum number of books to include in a single series? Three? Four? Eight?

To draw this comparison, it was necessary to normalize the earnings per book in each series, with the earnings for single, stand-alone novels by the same author. This needed to be done on a per-author basis, to filter out any differences in marketing strategy or sub-genre between the individual authors. Not all of the authors originally surveyed had stand-alone novels to normalize against. This therefore reduced the data set to a pool of 28 series from which to draw comparisons.

The results of this particular survey surprised me. It appears as if there is no practical limit as to how many books can be added to the same series - and yet continue to increase the net worth of each book in that series by a nearly constant factor. In other words, a series of 6 books will earn more on average than two series of 3 books each. This is true, even taking into account the previously mentioned trend between the number of books published and the earnings per book. Aligning the titles into a single series further drives up their marketability.

This was not an outcome I could have predicted, but one which definitely has implications for my own writing. I had planned out my own original series and story-arc to span four books in length, with opportunities for a couple of different spin-off series set in the same fantasy world. These results, however, suggest I would be better off including all of the spin-off novels under the same series label.