The agent’s answer
On this, Donovan draws a firm line between fiction and nonfiction. Nonfiction generally calls for a book proposal containing an overview, not a synopsis, and the two are not interchangeable: an overview is more zoomed out, leans on the book's optics, and goes into the themes, whether self-help or memoir, that the synopsis deliberately avoids naming. He notes the synopsis also skips editorial backstory and repeated use of the title, unless the protagonist's name is the title. On comps, the depth scales with format. A standard fiction query describes comps in a line or two. A nonfiction proposal, especially for a monograph or academic subject, can spend a full page explaining why a comp is comparable and what is original, down to publication, authorship, and performance details where they can be ascertained.