I like the idea of backstory, the offstage history of characters who appear in a narrative. Writers sometimes develop these in detail to help keep a story consistent, and to provide characters with a greater depth that can be hinted at in the story.
Genre writers take this idea and mine it for extra material, creating sequels and prequels and stories that go off on tangents with minor but beloved characters. I’m intrigued by Joe Konrath’s collaboration with Blake Crouch, Serial Killers Uncut, which began as a novella, eventually expanded into several interrelated but still standalone novels, and is now being released as a complete work.
Recently I read about in-app purchases, where you can expand an app right at the point of need for a small price, e.g. add a particular city map to your collection of maps, gain access to a new game level. And I wondered if there might be room for an in-ebook purchase.
Konrath and Crouch offer their interrelated books in different packages for different prices. But what if you could start with a central package, then add pieces at a small incremental cost at the point of interest. Intrigued by a particular character? Here’s a list of the other stories he appears in, some preceding the current action and some following, each of which fits neatly into the structure if you want it. Learn more about the characters or story threads you like, ignore the rest.
Fiction works well for this, but I think certain sorts of non-fiction could also make use of the idea. Perhaps there could be an edition of The Encyclopedia of Country Living with the general introductory content plus sketchy summaries of each major section. You could get an overall sense of what was available, then expand sections (e.g. food preservation, poultry) as you needed them and leave the ones that don’t interest you. And several of the books I’d like to write are interrelated. Perhaps it would be better to write it as one big book with sections that could be explored for a small additional cost if and when the reader is interested.