Dear David，
I’m writing this letter to express my sincerely appologies to you for losing the book you lent to me. I’m very appreciated you lent it to me. In order to give it back to you as soon as possible, I took it to the library yesterday.
I also borrow some other books in the library before I left. Unluckily, when I arrived at my dormitory, I couldn’t find your book. I searched all my dormitory and the road from the dormitory to the library. The next day I also looked for the library.
However, I couldn’t find your book. I’m sorry I can’t give back to you on time as I promised before. But I will buy a new one for you later.Hope you can accept my appologies.
Yours Sincerely,
Li Lei