We writers can get so caught up in worrying about finding an audience, selling books, and gaining recognition for our work, that we forget to love our work. We are our own first readers, and we should each be writing the book we would most love to read. That should be your test of every idea you have for a book and every sentence and paragraph and scene you put on paper. Do you love to read it? Is it the book you wish you could find in the library?
If not, keep trying until it is.