There are two views on writing trilogies. Write just the first book and see if it sells, and write the whole thing before your start querying.
My agent is of the "write one book first" camp. She advised that I prepare a synopsis for the next two books so she'd have something to show editors when she started submitting, but to start on a new and different book in the meantime. Her reasoning was that if the first book didn't sell, I wouldn't have wasted time on a sequel that wouldn't sell, and would instead be ready with a new book.
This is very good advice.
However, I've heard quite a few trilogy writers swear they'd never do that again. They'd rather write the whole thing first and then submit.
Having been through the process now, I understand their reasoning. And here's why:
Once you have a book written and out there in the world, you can't make changes to the story. Whatever you wrote you're stuck with. If you come up with a great plot idea in book two, you can't go back and add hints or groundwork to book one. (I suspect this would be especially helpful for a lot of pantsers who don't always know where the story is going to take them)
I found that was true with The Shifter. There was nothing major story wise I wanted to change, but little tiny things came up as I wrote the next two books, and it would have been so nice to be able to add them to the first book.
If you write the entire trilogy at once, anything you do in book three can be added to book one, and the entire series can be fleshed out as one story. Of course, the downside is that it'll probably take you a lot longer to get it done. This could be problematic if you have a contract to fulfill. Or if you're in a hurry to start querying.
You could always split the difference. A detailed outline or synopsis would help get the major points all aligned, and still let you write one book and send it out there. Some in depth character and world building notes can make sure you have a solid handle on how things work and how people live in that world. If the goal is to write one and then wait, the more details you can get down about the next books would be a tremendous help when you finally sit down to write them.
Which way you want to go really depends on the story and the kind of writer you are. You might now want to spend time on a long story, and are eager to get to another idea. But if you have a multi-book story idea that you feel passionate about, and it's an all or nothing deal for you emotionally, then maybe you'd be willing to invest the extra time and write all three before you start querying. (Though do make the first book a stand alone if you can. The odds are SO much better for you that way).
How do you choose? Ask yourself:
- Can the first book stand alone even if I never write the others?
- Do I need to see how it ends before I'll be happy submitting it?
- Do I know where the story is going or am I still figuring out the major parts?
- Do I have other stories I'd rather write or feel might be more marketable?
- Which way do I want to go?
- Will the trilogy be better if I wrote the whole thing at once? Worse? (Do I want agent/editor/reviewer feedback before I write the rest)
How do you feel about writing trilogies? Do you prefer to write them all at once or just the first book?