阅读下面短文，在空格处填入一个适当的词或使用括号中词语的正确形式填空。

Every summer holiday, I visit my grandparents in the country. Last year, I learned about an (usual) hobby on my way to my grandparents' home. It was a sunny Sunday. The sun shone (bright). I was on a train to my grandparents. There (be) a lot of people on the train. I (see) a man reading a book about gardening. I said to the man, "That seems like interesting book." He said, "Yes, it is a good book. But l am reading for a very special reason. It (have) a green cover. My hobby is collecting (book) with green covers." What a strange hobby! It is very hard find books with green covers. He spends a lot of time in bookstores. If he sees a good book with a green cover, he (buy) the book. Strange, you might say, but that's his hobby!