Reading helps us understand what is marketable before we spend hours writing something that’s not. So does talking to others in the industry, especially agents, editors, and publishers. Also, look at the publishers’ current releases.
As a starting point here are some general principles of what is not marketable. Though there are exceptions, they are rare:
- A book that’s too long or too short for its genre
- A book of poetry, unless you’re famous
- Your autobiography, unless you’re famous or infamous
- A book of short stories, unless you are an established fiction author
- A nonfiction book for which you have no authority or credentials
- A topic of personal suffering that many others have already covered
Aside from that, don’t chase trends. It takes about two years to have a book traditionally published, so by the time we write our trendy piece, the trend could be over, and no one will want our book.
Instead, write what you’re passionate about. Just verify it doesn’t fit into one of the categories of what to avoid. And then write it!