The Grimoire Library

It starts as a bad dream, and Norbert has been on enough antidepressants to know that nightmares come with the territory. Yet this one is different: It's too vivid, too focused. It's like he's awake. Dirty oil lamps hang from the ceiling on metal chains while black bookshelves run from one shadowed horizon to the next. He's in a library.

The dream ends with a book. Norbert finds a pattern and a word he recognizes, and the next day while bored in class, he replicates the drawing. The picture bursts into flames. The dream was real, and so is magic.

At first Norbert is happy, because if magic can exist, then so can change-he isn't stuck being depressed. However, happiness is soon replaced with dread when Norbert realizes the library isn't empty, and the spells he learns aren't safe.
Soon Norbert is afraid to fall asleep, unable to stop taking his new medication to free himself from the monster-infested library. Something there wants him back. And he's powerless to stop it.

According to the spiders, there are some things even magic can't change.