How To Write A Proposal Letter For Nonfiction Book . You’ll always want to review an agent’s specific guidelines and tweak. Most of a nonfiction book proposal is about your target market, platform, and marketing plan. EasySchmeasy Book Proposal Template Write Nonfiction NOW! from writenonfictionnow.com To get you started, here’s a rundown of the basics of a proposal: Here are some elements i love to see in a fiction book proposal (and if you’re writing nonfiction, most of these still apply!): Lecture 3 the role of the proposal in book acquisition.