When you meet this kind of girl you like in the library, you can find out whether she appears here every day in one way, then you can approach him by chance, and then you can have a chat to see if he is easy to talk to, so that you can get the contact information. Another way is to see what books this nickname reads in the library. If you happen to know this book, maybe you two can talk about your experiences. Of course, it is the best way for you to get to know him! This method is also very good.