What does Leigh write about in his second letter to Mr. Henshaw, dated December 3?

On December 3, Leigh writes the following year, saying that he is now in third grade; this year he read Mr. Henshaw’s Ways to Amuse a Dog, which was the first “thick book with chapters” he has read. Leigh says that if Mr. Henshaw answers his letter he will get to put his letter on the bulletin board.