Large Bent Handle

How well is Media Mail handled?

I'm about to ship four books to different people from bookmooch.com, and I know that media mail is the best service to use, but i was wondering how well they handle it (ex: will it be bent or torn) because my friend told me to just put the books in a large manilla envelope, but I'm afraid it's going to get ruined.

Media mail is theeeeee best
Have a nice week