I just realized something... There's a novella stand-alone story in my head that I want to write that, in-universe, is a prequel to my main fantasy. It's set when the main fantasy's MC (Mishu Jerni) is just 6-7 years old and accompanies the novella's MC through her travels. Should I write the novella first to (a) write a stand-alone story that I could get published and (b) develop the world and establish a firm backstory? The reason I say this is because while writing the main fantasy, I realized that the backstory I had for the main fantasy MC conflicted with the backstory that exists in the novella. In the novella, Mishu is a freed serf in a world where serfdom exists. In the main fantasy, however, serfdom doesn't exist for example. So...should I just put my fantasy series down and write that novella first? It might actually go easier because there's no possible 'sequels' hanging onto it; it has a firm beginning, middle, and conclusion.
Novellas tend to be a hard sell, so if you're thinking in terms of getting it published before the rest of the series, I expect you'll find it challenging. But if you want to write it, and then put it away for a while as you work on the larger series? Why not?
I'd finish what I was working on already but that's just me. And if your novella is a prequel for the main series I'd like to at least have the first book written and locked before I laid a potential landmine in a prequel, like what you said about the backstories conflicting between the two. Novellas are fun to write, but like @BayView said they're very hard to publish. You're essentially on the self-pub train with those.
What if I made it novel-length instead? A stand-alone novel? As far as publishing goes, I've heard that publishers really hate it when first-timers go in saying it's gonna be a series of more than one book. If I made this a stand-alone novel, then perhaps I'd have a better chance than if I wrote Book #1 of the main series and went from there. My thinking was that it'd make more sense to write this first to get a better understanding of the world and Mishu's backstory. I tried writing Mishu's story first, but it kept conflicting with what I had planned for the stand-alone (ie, serfdom vs. no serfdom) Hmm...good point. I think I may have fallen into that landmine already since in the main story, Mishu already knows who the MCs of the standalone story are, and they even appear as secondary characters a time or two. Maybe I'm just thinking too hard about this, I can just simply allude that they met each other before without going into too much detail on the exact events.
Well, I think I found a perfect solution thanks to you two: #1- The events of the prequel story happened, but I don't have to write about it. Mishu knows who those two people are, she has memories of what happened back then. #2- Mishu's 14 in the main story. During the 8-year time gap, serfdom is abolished. She knows she was born to serf parents, knows how she got freed, etc. Thanks.
Boom! Serfdom solved! I think they should all be able to stand by themselves, but I'm not a huge fan of series where YOU MUST READ THEM IN ORDER to understand what the hell is going on. I can't tell you how many series I've started, gotten maybe a third of the way through book one, and thought, "Damn, this crap goes on for another four books?" If it were just the one, I might have interpreted it differently, but once I sense that there will be no payoff for another half a million words I tend to tune out. It's hard to craft one compelling book, let alone three, four, or seven.
If you do decide to write the novella, you could always put it up on Amazon as a freebie to try to generate interest in your world, characters, and subsequent novels. If it is well-received, that could help you pitching the novel.
I accidentally wrote a short story prequel to my UrFan series and I'm trying to get my short story published even though I haven't finished the first novel yet. I'm just going to publish it as an "Easter Egg" and not as required reading. Like how Cujo didn't actually go on the rampage because he had rabies, he actually went on a rampage because his rabies made his susceptible to possession by the deceased serial killer from The Dead Zone, but you don't need to read The Dead Zone in order to enjoy reading Cujo. Reading The Dead Zone adds to Cujo, but not reading the Dead Zone doesn't subtract from it.