Yeah, that is called borrowing. I let my friend James read Day of the Triffids, which he read and gave back within 2 weeks. Even when it was in his house, it was my possession and would be for 9 months.
Anything that has been left in your house for that period of time with the knowledge and consent of the original owner automatically becomes yours legally after 9 months. Although to make the court case sound, I'd make documentation or evidence of dates etc.