1. Write a description
Basic, and elementary. If you can’t describe the book, whether it’s nonfiction, or a novel, the chances that you can write the thing are precisely zero.
For example, I once got an idea for a humorous novel. The central character didn’t want anything in particular — everyone around her wanted her to do something for them.
Luckily I wrote the description and spotted that. You can’t write a novel around a character with zero goals; there’s no conflict. All I had to do was give her a big goal.
Wondering how to be sure that your book idea will work? The above article will help.