When you are writing a book proposal, reviewers might be asked:

• What are the purposes and central argument?
• Contribution to the field and how significant?
• What is the competition? How do they differ to this book proposal?
• Are the premises+conclusion=argument sound and valid?
• Likely market?
• How can we improve it, in terms of style, weaknesses, structure?
• We may ask you to recommend 2-3 experts in the field who we will send it to..