Last time I mailed out a book I wrapped a couple of sheets of newspaper and then wrapped it in a brown grocery bag taped well.
Mailed book rate for $2.77 and plus delivery confirmation .80. The post office does mark the packaging MEDIA so everyone knows. I also think I read somewhere that if it's media mail the P.O. can open it to verify that it's actually only books (no magazines, etc.)
It's easy and cheap.