He's gonna be pissed when he finds out neither the book or coin is rare at all. The fact he thinks he was friends with Dennis Hof when anyone else can tell that Hof was just being cordial to a customer is instructive. He misinterprets normal social interactions as close friendships. That would explain why he was so pissed when Erika told him to go away. In his mind, she was ending a friendship when in reality she barely knew him. That also explains why he was pissed at Chad, he was getting in the way of him wooing Erika who was obviously into him or else why would she be talking to him? That would also explain why he thought the hooker he booked was his for real girlfriend. He doesn't grasp how daily interactions work. Hell, he thought Lindsey Vonn personally sent him a postcard for donating to her charity(or something, I forget the exact circumstances), so you know he's bad at interpreting normal people's actions.