A few days ago, I wrote about whether Criss Cross is a book adults such as myself like or a book kids like, too. Someone at child_lit tipped me off to The 'Criss Cross' Conundrum in School Library Journal. Karen Cruze, the author, isn't concerned about the adult/child issue but whether the book should be considered a high-end children's book or a low-end (meaning age) YA book.
Some people think such questions are nit-picking. But Cruze shows why they aren't. Books have to be shelved somewhere in libraries, and their classification determines where they will be shelved. And where books are shelved determines who is going to see them. Classification helps get books out to the people who are most likely to want to read them.
If Criss Cross is shelved with the children's books, but children find it too old for them, they won't read it. If it's shelved with the YA books and the YAs find it too young, they won't read it. Or, if it's a book that both groups would be interested in, a library might want to own two copies. If a library can't afford two copies...
Well, you can see why we're not picking nits here.