SCP Foundation: Iris Through the Looking Glass (Light Novel) Vol. 2

An unnamed boy encounters an inexplicable phenomenon–the same photo of a girl appears inside any book he opens. When one book in the library suddenly transports him to the SCP Foundation, a secret organization dedicated to containing anomalous entities and phenomena, he learns that the girl’s name is Iris–and that he’s going to have to work alongside her to get them both out!