I am terribly sorry to tell you that I have lost the valuable encyclopedia book you lent me last week. I read it every day and intended to finish it quickly. Last night when I came to my room, I looked for it in every corner, but it was not be found. I will try to recover it as soon as possible. If I fail to find it, I will get a new book for you.
But I am afraid it can never take the place of the old one. For this irrecoverable loss, I should be to blame. I was so careless with my things. I will be more careful in the future.
I like the book very much. It is a birthday gift from my sister. So I hope you can find it. I think it is still in the room. Don't worry about that, if you can not find it. Please be careful next time. In addition, if you haven't finished reading this book, you can borrow one from the school library.
You are a person who loves books so much, so I think this is not your fault. If the book is really missing, do not be sad for this. So you should stop the self-blame. Once found it, I'd like to send it to you as a gift as you are such a book-lover. You do not have to buy me a new one. This week I will visit the Xinhua Bookstore, and I will buy one again.