Dear Marcus,
I hope you have settled back in well after your flight home. I am writing to you today with a very red face because I have just discovered your copy of 'Advanced Macroeconomics' tucked away on my bookshelf.
I am incredibly sorry for this oversight. I honestly thought I had handed it back to you during our final study session at the library before you left. It was completely careless of me to pack it in my bag, and I feel terrible that you had to travel home without such an essential resource.
Could you please let me know if you need this book urgently for your current studies? I imagine it must be quite difficult to source another copy where you are, and I want to understand how much of an inconvenience I have caused you.
Since you are now overseas, I have already looked into international shipping rates. I am more than happy to post it back to your home address via a tracked courier service this week. Please send me your current postal details whenever you have a moment, and I will get it sent off immediately.
Best wishes,
Sam