There are many ways you can do it. 

You can certainly use a box. 

You can also wrap the books as usual, either individually or paired, etc. (what ever works for the size of paper) and then tape the wrapped books together (this works best if they are all of one size).  I've mailed up to 12 MMPs that way, wrapping three at a time and then taping the blocks together.

You can also fit the books together into a large bubblewrap envelope.  It is best to fold and tape  the edges so the envelope is tight around the books - the more they are able to shift, the more likely they will tear the packaging.  I girdle such packages both ways around with tape.

I do a lot of box swaps and with 4 books or less this is the way I do it:

Go to the dollar general store or Wal-Mart in the mailing section and pick up a roll of the brown thick shipping paper.  Stack your books together and wrap them in the brown paper just like you do a Christmas present then tape the holly c%^& out of it!  You dont have to use as much tape as I do, but I figure if I have tape over the whole thing then I know its not going to get damaged and its water proof.

Works for me, hope it helps.

O cut open a paper bag..the larger ones, if you still have access to them. They are free!!

I just put them in either manilla or padded envelopes. Just depends on the size.

You can use a cereal box if the books are all paperback. If they are not, you can use a small box either from a shipment you received through the mail or you may be able to pick one up from a store (if they are going to throw it out anyway). If the books are roughly the same size, you can stack them and wrap them together with plastic wrap then wrap them with a brown paper bag for shipping. Just a few ideas.......  hope this helps.

Shelley 

>When I print the label - If I choose to print a mass mailer label, will it automatically calculate the

>cost for all of the books packed together? Thanks for your help!

PBS  will make a calculation, but I wouldn't trust it.  I don't trust it even for single books.  Better to actually
 weigh the package and enter the actual weight.

>When I print the label - If I choose to print a mass mailer label, will it automatically calculate the

>cost for all of the books packed together? Thanks for your help!

>>>>PBS  will make a calculation, but I wouldn't trust it.  I don't trust it even for single books.  Better to actually  weigh the package and enter the actual weight.

I second that, I will go to ship a box and PBS will tell me it recomends 10.83...I take it to the po and it comes out to like 6 something.

PBS frequently has the weights wrong for books. So if you're not going ot the PO it's best to weigh them yourself.  PBS can't weigh every book posted so they go by the information they get from their outside resources-which aren't always correct.   Plus with publishers reusing ISBN's on a regular basis your book might not be exactly the same. 

For mulitple book orders I usually use whatever I have on hand, a bubble mailer, an emty cereal box or something. I've even saran wrapped them to form a block and then wrapped them up in thick paper.