Remus smiled politely at the man who had sat down on the other side of the table, reaching out and pulling his own books a bit closer in order to clear some space. Remus liked to spread out when he worked - during the creation of the Marauders map you hadn't been able to see the carpet of the Gryffindor boys dormitory.
He was just turning back to his book, scanning the page to try and catch the end of the sentence he'd been reading, when something occured to him. He should know that person. It was hard to tell - how could you ever recognise someone from this handheld muggle thing they were all carrying around? But Remus had to distinct impression they knew each other somehow.
"Erm.." he looked up from his book, leaning forward slightly apologetically. It was a library after all, and there were some rules. "Sorry, but... do I know you from somewhere?"