Do I need to have a book to trade with the indiviual when I order a book from a box-of-books member?

New horizons

If you want to do it as a BOB trade.  If you just want to pay with a credit then no.  Most boxer's still like to earn credits for WL books and books that they can't get in a BOB deal. 

And you have to have something they want, or they'll say no to any trade offers. So if you have a very small book shelf, or books that are plentiful in the system, you may get a lot of people not wanting to trade.

So it usually helps to have a large bookshelf for the other person to chose from.