Libraries and librarians are exquisitely sensitive to their community. They have to be. That's where their money comes from. Libraries have experienced a pretty massive sea change over the past twenty years as they went from "places that people borrowed books" to "places immigrants and the poor take their kids." They've become a social work project where people who studied taxonomy at school are suddenly helping ESL families fill out paperwork, protecting vulnerable children from abuse and becoming the Third Place for the disadvantaged many. If you walk around my neighborhood, we're white. If you go to my library, we're Somali, Ethiopian and Romanian. The books that are at your library are the ones that are being checked out by the people who are using your library. There's undoubtedly good content and the librarians can probably even tell you what it is but it may not be available without an interlibrary loan because for every copy of The Joke they've got to stock 30 copies of Twilight.
This reflects what I know about libraries. My mom was a librarian and if a system is at all well run it's responding to aggregate needs and desires of it's patrons. Libraries churn through a ton of low brow fare and also do a ton if work serving immigrent communities, job seekers, kids and the elderly. There is always the chance that your library is poorly managed. My Mom fought to buy 10% less of the shit you could get from a red box to spend some dough on more thoughtful stuff. A copy of Koyaanisqatsi will circulate a few times a year, a copy of Game of thrones will be in circulation as soon as it gets on the shelf. There are two compeating theories or at least there is balance that must disatisfy some people some of the time either way you go. You can go for maximum circulation and stock mostly stuff that's hot or you can currate a broader selection. It's expensive to give the people what they want. A hot DVD is garbage after a few months, popular books won't last a year.