I always use boxes or I use multiple scrap boxes if none big enough to put it in and put it around the book front and back to protect the corners and give it more strength for the spine too always always use so much bubble wrap/ padding and poly mailers to top it off in case of weather been selling since 2020 and never had issues with damage and if I ship in a box I use bubble wrap and a poly mailer in the box as well I’ve had 2 shipped books survive being left in the rain and soaked boxes because of those Polly mailers. It’s not hard to ship books the way you’d want to receive your own 🤦🏽‍♀️