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Yes, you can wrap as many as you need or even use a box. Just make sure the postage covers the weight. Over 13 ounse needs printed postage or brought to the post office.

If you have prepaid postage with PBS or Paypal or similar, then you don't  need to go to the PO, regardless of the weight.

You can drop these off at any blue box or give/leave to your mailman. 

Welcome to PBS Alyson!  And yes you can wrap multiple books.  My personal maximum is two average size mmpb when using the PBS mailing label alone, after that I prefer a sturdy padded envelope or a small box (recycled :)

Yep...I just sent 4 books wrapped together w/o problems. Just remember if you don't use a box, make sure they are well wrapped in plastic and  freezer paper or brown wrapping paper. I have a roll of plastic about 6 ins. wide. I wound it around the books about 12 times around the lemgth of the books and another 12 times around the width of the books. Then wrapped the whole thing in  double thickness of freezer paper. I had to take the package to the mailbox with the bigger opening. The thee inch wide opening at the P.O. mailbox just wasn't going to cut it.

Like Sue, I also stablize multiple books together before appliying outer wrapper.  I place the receiver information (or duplicate mailing laber) inside the package in case of USPS emergency.  I then wrap in Saran (or other plastic underwrap), and make a couple wraps around the books with packing tape to firm up and support them during shipping.  Outer wrapper is applied over this...seems to work well 

I recently sent two books that I wrapped in a grocery bag and then wrapped in brown paper. One of the books was a hardcover textbook, the other the answer guide for the text book.