A thing I run into quite frequently (read: daily) at the library is a fear of genre. It's okay to have your reading preferences; I certainly do. Myself, I don't read a whole lot of mysteries. It doesn't mean I won't, but rather they aren't the books getting my attention. We all are more than allowed to make those choices. But what really gets me is people making those decisions without having ever even put a toe outside their comfort zone, or people making those decisions even when it's an author they're familiar with.
For example, Dean Koontz has his Odd Thomas books, right? One of them came out at a graphic novel and only as a graphic novel. Patrons who reserved it by merit of it being Dean Koontz and Odd Thomas, like you do. An unmeasured percentage of them, once they saw it was a "comic book", said "Oh, I don't want that" with a particular wrinkling of the nose and returned it unopened. Didn't even leave the building with it.
John Grisham has a series based around Theodore Boone, a 13 year old lawyer. Across the libraries in my system, that might be shelved in Young Adult or might be shelved in Juvenile (what we call MG). People come in asking for the new Grisham, or for that Grisham in particular, and when they find out it's "for kids", there's that nose wrinkle again. By the way, J is where we shelve our Harry Potter and Y is where our Hunger Games are, and people will check those out, typically after they've seen the movie. Seeing that currently with the Veronica Roth Divergent books.
We actually have a display right now, of subgenres, inspired by a conversation I had with a patron who was taking out Boneshaker, by Cherie Priest, and had never heard of Steampunk. She didn't end up liking it, but I thought it was cool she was interested and willing to give it a try. There are people who come in looking for The Curious Incident of the Dog in the Night-Time, and when they discover it's a mystery, some don't take it. There are people who come in looking for Ray Bradbury, or Ursula LeGuin, and are put off when those are in the Fantasy and Science Fiction section.
There are the people who think Fantasy and Science Fiction should be shelved separately, because they aren't the same thing. There are people who are confused (I'm in this camp) by the fact that we shelve vampires, zombies, and Neil Gaiman in the regular fiction.
We have limited space at my library, and the catalogers aren't all familiar with genre. But it genre an all or nothing prospect? I don't think so. Gabriel Garcia Marquez, say, doesn't necessarily belong in the Fantasy/SciFi section, but he could fit there. Ray Bradbury could be comfortably shelved with the "regular" (literary and commercial) fiction. The time travel romances (with or without highlanders, but really, why are there so many Scottish Highland time travel romances? When did that become a Thing?) aren't in the SciFi, nor is H.G. Wells, but we have one Lovecraft there and the other in regular fiction.
I kind of wish my library would actually just Dewey Decimilize the whole damn thing. Just assign each book its number and let people look for it by merit of that, not by the fast-and-loose genre categorizing we're currently doing. You want fiction? It's in the 800's, then look for the author's last name. Done.