Which book that make you happy in English?

I ever read one book that make me very happily so much. I love to read it because it's Love Letters of anyone. Some letter like my feeling with someone, she fall in love with a man but she never told her secret love to him. I love to read all love letter because when I read it I felt like a man or a woman. I think we choose fine some book that make us happily, moreover it help us to improve reading skill. I always think that I hate to read the book but this book was changed me love to read it. Now, I make it lost I cannot find it. I love that book so much. To know some information be reading is make us feel better more than listen from someone.