The leader of the library thinks that all the books in their library are better than everyone else's books. He's a very biased person. If he wasn't the leader of that specific library he'd probably feel differently.
You decide to give in to his biased recommendations and look at what he has in his library. It doesn't take long until you realize that these books are all about hens (へん) and hen care. This guy is so biased about his favorite books that he only filled his library with what HE wants to read. And apparently that thing is taking care of hens... weird.