A lot of writers here blog about the difficulty of trying to fit their work into a convenient niche. I didn't get the concept of niche marketing at all when I wrote my first novel; I just wrote a book I wanted to read. When prospective agents asked who my target market was, I would say, "Um...women who read?" I wasn't trying to be disingenuous, it just never occurred to me to set any age or genre restrictions on the potential readership of my book.
So I was a bt flummoxed when Booklist rated my historical novel YA (Young Adult)/Mature. Not that there's anything wrong with that. The YA classification doesn't dim the lustre of the Harry Potter oeuvre, and everybody reads them anyway. (It's always funny when a new fantasy epic is hailed as "Harry Potter for adults." Everybody knows Harry Potter IS Harry Potter for adults.)
But it was never my intention to write specifically for the YA market, and I'm still not sure how the designation came about. Yes, The Witch From The Sea is a coming-of-age novel, but of an unorthodox sort, as my heroine runs away to sea in male disguise ca. 1823, and ends up on a pirate ship off the coast of Cuba. Or it may have been the presence of pirates in the story at all, universally assumed to be the exclusive cultural province of little boys. (Although in my book, the pirates are metaphor for the freedom my heroine craves.)
Or it may simply be the fact that my protagonist is 16 years old when her adventures begin. A friend of mine writes a bloody, two-fisted adventure series set in the fledgling days of the U. S. Navy. Although laced with plenty of dark humor, the books are rife with corruption, cynicism, racism, and wanton violence — not exactly for the kiddies. Yet, because his protagonist is 17, he often finds his books categorized as YA.
The more readers, the merrier, of course, and if young adults are encouraged to read my book, great!— as long as there's not a concurrent backlash among potential readers who categorically refuse to read YA. Another unforeseen problem is that when my book was classified YA, I was suddenly thought to be an authority on the YA marketplace. At a book conference a couple of years ago, I was invited to sit on a YA panel, whose audience was mostly mothers and their 'tween daughters. Since the moderator had prepared a list of category-specific questions (beginning with "Why do you choose to write YA?"), there were only a limited number of ways I could participate in the discussion. The other panelists were YA veterans who wrote contemporary, issue-oriented books, but I chimed in where I could. Issues of self-esteem and identity are perfectly applicable to my heroine. Internet bullying, not so much.
My new novel, currently at the agent's, is fantasy. It's protagonists are definitely grown-ups, although it does take place in the Neverland. Is it YA? Not intentionally, but then I'm always the last to know.