I finally stopped losing my books by writing my name inside the cover, and it worked
I lend out maybe 6 or 7 books a year to folks at work and used to lose track of them all the time. Two summers back I started writing my name and the month I bought the book in small pencil on the inside cover, and I got 5 of them back in under 3 months. Now when I swap a book here I just tell the person it is pencil so they can erase it if they pass it on. Anyone else mark their books before trading, or do you just let them go?