Dear Frank,

　　I'm terribly sorry to tell you that I have lost the book you were so kind to lend me last week. I like the book very much and I read it every day and plan to finish it next month. Last night when I came to my room, it wasn't found anywhere. I will get a new book for you.

　　Old books are like old friends. Once they are lost, they can never be replaced. I feel sorry for losing the book. I was so careless with my things. This is a warning to me to be more careful in the future. Best wishes.