Are some ideas worth a full-length novel and some not? Are some best for a flash fiction piece and some for a fully developed short story? What does it take to flesh out an idea and make it worthy of an 800 page novel?

It’s clear that “What if the moon blew up?” is a popular question right now. I’ve seen it in several places in the last couple of years. One was last year’s short story “Goodnight Stars” by Annie Bellet, who withdrew it from the 2015 list of Hugo finalists. This is also the question that generated this year’s hard SF blowout Seveneves. It also appears this will become an issue in N.K Jemisin’s The Broken Earth series that The Fifth Season kicked off. It’s a popular idea because it’s a weighty, catastrophic event that opens up a lot of scenarios. You can expand it to different lengths without much trouble, from short-short to an 800 page novel.

Regardless of whether you’ve come up with a weighty, catastrophic idea, though, you have to have the skill to keep the narrative of your story running and interesting enough that the reader will 1) keep reading and 2) enjoy the book enough to buy your next one. Clearly, this gets harder as the story gets longer. The author has to be able to manage the complexity of different characters and their subplots, besides the issues of world-building and technical accuracy, plus keeping a finger on the pacing and how the story develops. Readability is important for customer satisfaction, so the end result needs to be understandable and entertaining. It would also help if people like at least some of your characters.

Is there a most comfortable length for a book? Patricia Briggs, I notice, cuts her best-seller urban fantasy books off at about 350 pages. This is quite a bit shorter than what I’ve been reading for the awards, and it feels like a comfortable length. Normally Briggs had plenty of space to use on the characters and their relationships. It allows for plot development, along with whatever subplots she might have going on. However, it doesn’t require a huge idea and doesn’t drag the story out to the point where she’s having a hard time sustaining it; for example, having to add filler material, or where she’s losing control of the interactions, pacing and theme. I can read a book like that in a couple of evenings. It feels good.