When I return a book I put it in a bin, and a (non-Jewish) worker later takes it from the bin, and scans it into the computer as "returned." As such, can I return a library book on Shabbat?
Assuming that you know 100% a non-Jew will be on duty, and assuming that scanning books is forbidden on Shabbat.
I think it would depend:
That said, it sure doesn't seem Shabbas-dik to be returning books on Shabbat.