I have a book that was requested today that has a CD that comes with it.  I'm worried about the CD breaking in transit.  Should I put this in a box? And, if I do, will I still be able to send it via media mail, or would another method be better? 

You can definitely send it via MM but that is a slower class of mail.  You may find First Class Parcel isn't that much more and should move your book/CD along faster.

If you're worried about the CD breaking, find a small box for the book or get a padded envelope to mail it in.

I mail audio cd's all the time.  I use a padded envelope.  It is media and can be sent media mail.  So choose whichever is more economical for you.  If 1st class is only a bit more than I use that, otherwise MM.

The padded envelope is a good idea, but would add another week before I could mail it. 

I have a couple of Amazon boxes around here somewhere that will work. 

I'm clearing out my computer books and they are big, heavy ones, most with CDs.  I hope I don't end up having to remove some of them because I don't have the stuff to mail them!  I'm not sure a padded envelope would be such a good idea with some of these really big ones. 

More pondering to be done . . .  :-D

Thanks for the help! 

Cut a piece of cardboard the same size as the book and tuck it in behind the cover that has the CD.  A stiff, thickish piece.  Tha will provide protection against bending & against poking.

Kayote --

Thank you!  I don't know what happened to my brain, but my problem solving skills are deserting me right now.  I *so* appreciate the help.  That is a great idea! 

Thanks!!