I heard someone say once, write 5-10 different version of the same blurb, then narrow down from there. I agree. Narrow down to 3-4 and share with people you know who read. Ask them, “Which one would make you want to pick up this book?”
I have never done this step early, but I do agree that, just like writing your elevator pitch early, it will help you focus as you write. Or when you’re editing, it will help you know what you can cut.
The back-cover synopsis lays out the book’s premise and piques reader interest. Here’s how and why you should write one early and often.