answer: Edward is excited because he thinks it's a good way to put books on the subway for people to kill time.
documents: #Person1#: Why are you so excited, Edward? Is there anything happy?
  #Person2#: Of course. Not only happy, but also meaningful. I took the subway to school this morning. Iin the subway station, I saw one novel lying on a seat there and another near the elevator.
  #Person1#: Really? They must have been put there by someone for sharing.
  #Person2#: Yes, I was curious in red one. What a good way to kill time on the way. I plan to put my book there, too. Just for sharing.
  #Person1#: Great. But please, place it in a proper place and don't bother the traffic.
  #Person2#: OK, I will.