You Must Be an Acknowledged Authority
You have seen that writers of nonfiction should have some familiarity with their subject matter. For the most part, no more than this is required to write nonfiction. But when a writer proposes a scholarly nonfiction book, the publisher does not expect it to be a training experience for an apprentice.
Even though you possess substantial knowledge in the subject of your proposed book — perhaps as much or more than most authorities — your command of the material will not satisfy a publisher. It is necessary for you to be a recognized expert, generally with the most advanced degree obtainable in order to write a scholarly book.
Although a number of university presses carefully scrutinize the manuscript before it ever goes to production and frequently circulate the proofs for comments by other experts, many publishers do not undertake this review for a variety of reasons, not the least of which is the cost factor. Consequently, publishers rely on the author's representations that the book's content is accurate, which can be best ensured when the author possesses the appropriate credentials, such as a PhD in the field.
There can be instances, however, where your learning experience might result in a scholarly book. For example, it is not unusual for a doctoral dissertation to be expanded into a book that may even reach beyond academia. This occurred with Hitler's Willing Executioners, by Daniel Jonah Goldhagen, which grew out of his doctoral dissertation to become a bestseller.
