From Writers Helping Writers:
Many authors would rather write a whole new novel than cram the one they’ve already written into a five-hundred-word summary. If I wanted to write a short story, I would have written one. Right?
The reason we hate writing synopses is because they’re hard. The reason they’re hard is because, more than any other tool available to us, they show us what’s wrong with the novel we’ve labored over for months, if not years.
The synopsis is the equivalent of a house inspector—that man or woman who walks around with a clipboard and goes through the house you thought you were ready to sell, pointing out all the structural issues you either didn’t know about or pretended weren’t a problem: roof damage, termites, a saggy bearing wall, you name it. You can do all the fancy writing in the world. If there’s something fundamentally wrong with your novel, it will come out in the synopsis.
That’s why we hate them.
That’s why most agents ask for one.
Reading a synopsis is the quickest way to know if a novel will work or not. It’s also the surest way to find out if the author knows what they’re doing when it comes to things like structure, causality, story arc and characterization—you know, those critical developmental issues you hoped wouldn’t matter.
Guess what? They do.
If your plot is anecdotal, it will show up in the synopsis. If your protagonist doesn’t have a goal that they’re actively pursuing throughout the story; if there are no stakes, a weak antagonist, a plot that’s bursting with too much superficial business and no depth—yup, the synopsis will reveal all of that.
If you, the author, are willing to see it, the synopsis will be that heart-sinking moment of truth where you can no longer deny that this house is not ready to sell, not by a long-shot. It needs help. It might even need to be razed to the ground.
Link to the rest at Writers Helping Writers