How Do I Know What I Think Until I See What I Say?

I've been working on the TNP for a while now, and this week a sudden and horrible thought came to me -- what if this book is unsaleable? NOOOO! I don't write with an eye toward selling necessarily. I don't make character choices or plot choices or language choices with an eye toward "the market" or "trends" or what have you, especially not in first drafts. I write what I would like to read. But still, since I'm in the middle of the query process with The Book, the question crossed my mind. See, The Book fits squarely into a precise genre and subgenre. It's a fairly original idea (in my mind, anyway) and excellently executed, OF COURSE :) , but there's no question where it would go in the book store. But the TNP is not of a type that I've seen before. It's ... less specified. And so, as a result of the query process, I started getting concerned that the TNP--which I am writing, you may recall, as a hedge against The Book not s