@Sophia Pang,
He used "pang" and "punk" because your name is pang and the other person who responded calls themselves punkey.
We can all see what your name is, you have it written right out there.
Re your question, the word "volume" is used to distinguish one book from a collection.
The word "reflection" is talking about when you think about something from the past, that you learned a lesson from. You "reflect" on it.
It's a play on words as in "Thinking about the books you have read"