The Boy in the Striped Pajamas by John Boyne

Cath is a Simon Snow fan. Okay, everybody is a Simon Snow fan, but for Cath, being a fan is her life. Cath’s sister has mostly grown away from fandom, but Cath just can’t let go. Now that they’re in college, Cath must decide if she’s ready to start living her own life. But does she even want to if it means leaving Simon Snow behind?

Cath doesn’t need friends IRL. She has her twin sister, Wren, and she’s a popular fanfic writer in the Simon Snow community with thousands of fans online.  But now that she’s in college, Cath is completely outside of her comfort zone. There are suddenly all these new people in her life. She’s got a surly roommate with a charming boyfriend, a writing professor who thinks fanfiction is the end of the civilized world, a handsome new writing partner … And she’s barely heard from Wren all semester!