Elizabeth Wein, on book categories.

From Writing Teen Novels:

I think that organising books by their intended age is ghettoization.  It leads to further micro-classification that I just flat-out object to.  In the local library in the city where I live now, two of my favourite authors, K.M. Peyton and Robert Westall, have their books split not just across two sections but across separate shelves labelled Horse Stories, Times Past, War, Supernatural, Family, and probably something else I’ve forgotten.  When I first read Peyton’s books, I read them all because I found them next to each other on the same shelf.  I’d never have gone looking for horse stories.  I read them and I loved them because I loved that particular author.  I think that breaking up books into this many categories creates narrow-minded readers.  There is no incentive for the lover of ‘humour’ ever to look anywhere else for reading material than the limited ‘humour’ shelf.  There is some very funny science fiction out there but they’ll never discover it.

Well, that's where cross-shelving comes in.

(I certainly understand her POV—and that's actually exactly why I dismantled the Newbery Section at my library and interfiled the books into their various larger sections—but libraries and bookstores have to take into account how their patrons look for books. And a lot lot lot of them want to browse through sections of readalikes. Anyway. Regardless of whether or not I agree, I do love reading about various readers' personal browsing/searching/shelving preferences.)