This is a trick question, because there's no simple answer. You might not have more than one novel to try to sell. On the other hand, you might have more than one idea, and be wondering where to start first. Or, you might have had an idea that you've been working on for a long time, and you might have come up with another one just to challenge yourself, to see if you have more than one idea (this is what happened to me).
So you know, I do have more than one idea. But the fact of the matter is I have one CORE GIGANTIC IDEA. My core gigantic idea is Varin. I've developed it for nearly thirty years. And yes, I have other ideas - I have another whole novel all written, in fact - but the fact remains that Varin is in my heart.
So what does this mean?
Well, because Varin was my big idea from the beginning, the first novel I ever tried to sell was a Varin novel. And it wasn't ready. This should come as no surprise to you internet experts. It needed more time. I needed to write more, and I needed to solidify my craft and develop my voice and all that. One of the ways I did that was by testing myself to see if I had any other ideas.
I did. I had a really good idea, that turned into a pretty cool novel that I still really really like. But at this point I'm realizing I may have been lucky not to sell it when it was ready. Why? Because one's debut novel should be indicative of one's future career writings. The novel with which one woos an agent should be indicative of the path of one's future, so that the agent knows what he or she will be representing in the future. After all, you want your agent to be ultra-excited about you, and that means having your agent be ultra-excited about what lies at your core.
So here I am, and I finally have a Varin novel that really does Varin justice. And I'm realizing, not only that this is what I should sell first, but that it is what I should always have planned to sell first. It represents not only a bunch of work on a cool idea, but an entire world in which there are more stories than I can count. It's a little scary. Maybe a little like having all your eggs in one basket. But I believe in Varin, and I need to try my hardest to make it work.
So what does this mean for you?
I'm not sure, but I think it means that you have to follow your heart. You have to identify what you love, love, LOVE to write, and write it. Make sure you don't decide it's "done" and can't be improved, though. Don't be afraid to revise. The book you want to write - the book that everyone will love as much as you do - is out there, and if you keep imagining, and you keep looking, and keep working, you can find it. It's hard to wait, I know. Ten years ago I was already thinking, "I want to be published now now now!" But I think it's better to be standing here, unpublished in novels and holding in my hand a novel that I truly love, than to have set the wrong expectations in the first place.
It's something to think about.