Eee, double clandestine public wankery FTW! I love that Percy knows what Hermione's doing, and that he joins in. Even though "hot" is not a word I generally associated with Percy, he's definitely sizzling here.
Percy’s blue eyes sparkled and his feet nudged hers under the table.
“Hermione,” he growled, clutching at the parchment convulsively with his free hand.
See? Totally hot. Guh.
The library is the perfect location for these two, isn't it? Great job.