Since he's had your books for 3 months, and is evidently able to ship other items with no problem, I would proceed in the following way: First, I would send him a text and tell him that you want a photo of him, with both of your books and a copy of today's newspaper, because at this point, I would be concerned that he may not have the books anymore. I would also let him know that if he can't or won't provide this photo within your time frame, your next call will be to the police department in his city and have him charged with theft.
I pray it doesn't have to come to that. Let's see what happens tomorrow.