As writers, it seems we're always thinking about sequels. Should this story have one? Or five? Maybe there's room for a "companion novel." Or a prequel.
Sequels can be so fun—you already know the characters and it's like hanging out with good friends instead of trying to make new ones. But there's stuff to consider when choosing whether or not to stay in a particular story. It's not always a good thing. In fact, I might argue in most cases it isn't the smartest move.
But here are some questions you can ask yourself. Hopefully they'll give you a clearer idea of whether or not you should write out a sequel (or a whole series).
Do you have a multiple book deal?
I know, very simple question, but humor me here. The only sure way a sequel will be published is if a publisher has already contracted to, uh, publish it. Your sequel (or series) should be at the forefront of your writing focus at this point—those books WILL be coming out and you need to write them.
Do you have a book deal?
Sometimes a publisher will be open to buying a sequel (or companion or series) if your first book does well. If you have a book coming out, a book with sequel potential, you could definitely justify writing that sequel and seeing if your editor likes it. If they don't, it kinda sucks, but at least it has a chance.
Do you have "prospects" for your sequel?
Maybe you have an agent, or perhaps a publishing house is interested and asking about sequels. You get that itch to write—is it okay? Maybe. Consult your agent. I'm pretty sure mine would say hold off, but I know every agent and situation is different and maybe that publisher would want some sample pages, etc.
If you have no "prospects," why are you writing a sequel?
Is it because you're high on the story and want to keep going? Is it because you're afraid to move on because you don't think you have other good ideas? Is it because you are 100% sure this book will sell and people will be begging for more immediately? Or perhaps you feel like you don't know where the story ends, and you need to explore the world/characters more?
Whatever the reason, really think about it. Think about if it's worth the risk. Choosing to write a sequel is even more risky than writing that initial book—it's a book that essentially has no chance to sell unless the first does. It's a book that can wait if you have other ideas.
What are the emotional consequences of staying in that world?
Confession time: I've started writing two sequels and have actually finished a whole third one. From this experience, I've learned that writing a full on sequel only gets you more attached to your characters and world.
Which makes it much, much harder to let go of that world when a book fails.
I thought my dragon book was The One. I had many requests from agents, so I thought I better hurry and write that sequel. And I did. It was so awesome, too (okay it was actually horrible and I'd rewrite the entire first book and scrap the embarrassing sequel for something way better).
But when all of those requests turned up with "great idea, clunky writing," it hurt more. I'd invested more into "the series" than I really should have, and it made it harder to walk away, move on.
Are you prepared to change a vast amount of your sequel material?
Okay, say you write those sequels—say you write the whole ten-book series—and then you DO get an agent for the first one! Yay! Awesome! But what if your agent has a very different idea for how the other nine books should go? What if you show them what you've written, and they suggest HUGE changes?
Or what if your agent starts shopping that first book, and an editor takes interest, asks for sequel ideas, and then HATES what you have? Maybe they want the first book, but want to change the rest of the series. Are you okay with scrapping all that work? It depends on the situation, of course, but you have to consider the idea of potentially throwing out everything you've done.
Are you okay with the possibility of the work going nowhere?
It's totally okay to explore. I am a fan of exploratory writing—I wrote a Steampunk book for that very reason last year. But at the same time, the second I start loving something I dream about publishing it. It's hard not to! But still I try to enjoy my exploratory writing, tell myself it's just for fun and learning. There is nothing wrong with that.
So those questions probably sound really harsh. I guess they are. But if you are seeking publication, part of that is thinking practically. Working on sequels is often not practical. There's a time and a place for them, and you need to decide when that is.
I know this is when some people may argue that it's okay to write a sequel that stands on its own as long as it really is a fully separate story. True, but that can be hard to do and I don't think most people think of sequels in that manner. And that would mean you're basically writing a "first book" anyway. Why not try a different story?
Most of the time, it's a better idea to move on to a new project unless you're sure that sequel is worth the time and emotional investment. But if it is worth it to you, then by all means go for it!