How much should you lie, er, exaggerate in your book proposal?

How much should you lie, er, exaggerate in your book proposal?

Honestly, I’m in favor of the absolute truth in nearly all things. However, when it comes to a book proposal that you send to publishers and agents, you are describing a book that likely doesn’t yet exist. (You didn’t make the rookie mistake of writing the whole book before pitching it, did you?) You are…