Would you mind crosspost this on !dumpsterdiving@slrpnk.net?

This is a very good content and work you're doing here. Some textbooks goes quickly out of date. After 3~5 years some aren't relevant enough to be still bought them rather that the last version so they cannot be handed down so much but a few hands down of a book can help so much financially. And there is still plenty of use for an out-of-date book.