on Jane Friedman site:
Writers often dread writing a synopsis. After carefully composing scenes, fleshing out characters and establishing relationships, now we’re supposed to summarize the whole thing in under two pages? Plus, the stakes feel high. If a literary agent doesn’t love the synopsis, will your book ever reach publication?
But writing a synopsis should be done long before you’re ready to query agents. More than just a tool to sell your book, your synopsis is a roadmap to the next, stronger draft. After reaching the end of your manuscript for the first time—whether the process took 30 days of NaNoWriMo or several years of your life—sit down and write a synopsis.