Libraries often feature in fiction (Harry Potter - Hogwarts is the obvious example). Characters are seen researching, sometimes reading for pleasure and so on. In my Fairy Kingdom the bigger towns have bigger libraries but even the villages have their own library, albeit on a smaller scale. Oh and nobody would dream of shutting libraries to save money. This is how you can tell I write fantasy!
Which of your characters is heavily into books? Are they teased or despised for it (incredible as it may sound but not everyone appreciates the value of books!). What books are banned in your worlds and why? Can specific people groups only read books that are suitable for them? Answering these things fills in more knowledge about your world setting and how it works and that will strengthen your story.