I could put him the spare room and get him to sort out my books for me....make him arrange them alphabetically by author...or something equally cruel!!
That's something I used to do with my own book collection, when it got big enough to need that level of organization.
Yeah, lending books is something I don't do anymore. If someone wants to read something I have, I'll mention the library, Amazon, Chapters, one of the local second-hand places, eBay, or whatever.
Some of what I let others borrow have proven to be extremely expensive to replace, and some of it is not replaceable at any price.
Over the years as I've moved around, a couple of landlords have asked if I'm setting up a lending library (when you have several dozen bookshelves and thousands of books, they sometimes get that impression). I tell them no, I don't lend books, and the reason I have so many is because I've been collecting for most of my life.
Then comes the question, "Have you read all of them?"
The answer: No. Of course not, because one of the reasons I bought them in the first place was because I knew the time would come when I wouldn't be able to afford new books, and I wouldn't be stuck for something new to read. It really is like a personal library here, with fiction, nonfiction, media, and everything separated as best as can be managed (had to put some books where they fit, not with the rest of the series or category where they should be). I used to work in a library a long time ago, and habits don't really die. At least I have not gone as far as putting little tags on the spines with their Dewey Decimal numbers on them, although I remember exactly what some of them
should be.
I don't buy many new books (or used ones for that matter) anymore, for a variety of reasons. The last books to come in here are reference books on historical costumes and clothing worn by people from ancient times to (sort of) modern. This is because I needed some guidance on what the medieval-era characters in my now-very-large NaNoWriMo project would wear, what it would be made of, and how it would be constructed.