One my associates made the comment about how hard it is to sell unique story ideas. It seems like Hollywood, publishers like to stick to tried-and-true subjects that have sold in the past. You know like Hang Over 2. Problem for the writers is that it forces them to stick to retread topics or form a highly persuasive marketing proposals within their book proposal to persuade publishers to take a leap of faith. When you're already working in a highly competitive area, asking a publisher to leap and possibly fall isn't always a persuasive argument.
When I decide on a book, I always base it on a little bit of gut and a little bit of knowledge about the marketplace. For example, when the Fertile Kitchen Cookbook authors approached me, I considered my own experience with infertility. I remembered the hunger for knowledge and solutions -- and the library I accumulated. Knowing that couples experiencing this sort of crisis would also be just as hungry for knowledge, I knew that book would do well -- and it has done very well. When I read A Feast at the Beach, I saw the potential if the author would do two things. Change chapter 1, which broke the tone of the book, and add the recipes at the end of each chapter. This decision would also increase the page count, as the book at that time was too short. My gut told me people would love the charm and magic of the book -- and the escape to Provence through the eyes of a child. I was right.
These decisions are also made (for me) based on the material. I need to personally like the material. Other publishers with more to risk than 3L Publishing will not use their collective guts to make choices. They will be much more business like and do a lot more analysis. Truth is, you can analyze the market to death and that will only get you so far, because the buying public is finicky. If the publisher of Harry Potter hadn't take a leap of faith, Harry, his friends and author JK Rawling would not be clinking champagne glasses together over their $500 million box office winner. And Rawling, a former single mother on the dole, would not be one of the wealthiest authors on the planet.