I have seen a lot of people who struggle to decide if their book should stay as a single novel, or expand into a trilogy or series. Here are my suggestions:
>> Could you go farther with this idea? In the Hunger Games, Suzanne Collins could have left the tale with Katniss (spoiler alert) winning the games, and it probably still would have been a big hit. However, she decided to make it a trilogy because she had developed the plotline enough to do so. Ask yourself: Could your character go on another adventure/another date/another battle?
>> Know when to start fresh. Sometimes, you have stretched your story so thinly across a trilogy or series, that you have to call it quits. If anyone has ever read a very large series (such as Warriors by Erin Hunter) then you know that by the end of the last book in a sub-series you could tell that the author(s) were ready to move on with a new idea that they had been cooking.
>> Start planning. If you decide to expand upon your idea, map it out. Even if it’s a very light sketch for an entire series, at least have a blueprint so the protagonist is not blindly stumbling about to face an unknown antagonist.
If you have any tips, questions or comments about novels, trilogies, and/or series, please comment below for the benefit of others.