Severus gave Weasley a flat, disinterested look. Whatever had possessed the boy to think Severus cared whatsoever for his choices in literature was beyond him. And it struck Severus as a plea for conversation, the inclusion of 'embarrassing' in Weasley's description of his book. He wanted Severus to ask what it was. He probably wanted the chance to admit to reading some pornographic novel, and they would both laugh about it, Severus would poke fun before whipping out his own stash of worthless books, and then they would end up best friends forever or some rot.
Was that how Gryffindors formed most friendships? Bonding over porn?
"What are you reading then, Weasley?" Severus drawled. "A self-help manual? How to Learn Everything There is to Know About Your Neighbour?"