I need help with the best way to post a box set of books.  I know I can't post it as a set and get credit for all 3 books.  They are all in like new condition and more than likely on wishlists.  If I can sell as a set I can include the box and a small poster that was included.  I think the best option is to post to the 'book bazaar' forum, but I'm not sure what to do if someone is interested.  Can I post the books and specify the recipient, if so how do I do that?

Check the ISBN for each. If they're all WL then you can use the July WL multiples thread in the Book Bazaar forum to post them. You have to list them there separately and indicate how many wishers. Check out the rules there and it's pretty easy to do that. You'll need to state in your post that you want to send them all to one wisher.  The extras would make it enticing, but you might not be able to use media mail if you include them.

Another thing to do, if you don't want to use the WL thread in the Book Bazaar is actually post the first one and see if the wisher is also wishing for the others. I've actually done this a few times and though a couple times they didn't have the others on their WL, I sent a PM to ask them if they wanted them and if so to put the ISBN on their WL. The odds are higher that someone wanting the first one will also want the later ones versus someone wishing for the latter also wishing for the earlier ones. But if they don't you're still obligated to send the book you posted, so that may not be an option for you.

 Can I post the books and specify the recipient, if so how do I do that?

What you do is go to their wish list and post directly to it. When you are on the wish list page, hover your mouse over the button that says 'Post This Book' and it will say "Post this book into the system for this member." You will have to do it for each book separately.

If the box itself has an ISBN# (usually a barcode), then that number will be for the set and will be different than the individual ISBN barcodes on each book. You could post them with the set ISBN# without having to create a thread or post in the Bazaar forum.  You would only get 1 credit that way.  In so doing, you probably wouldn't know in advance who to send it to unless the box ISBN# shows a friend that has it wishlisted.

Also, if only two of the books are wishlisted but you find someone who does want all three, you can post the book on your bookshelf and they can order it directly from you. They will need to order it directly from your bookshelf, using the Order This Book link. If they do it from the book page and not your bookshelf, it will just go to the first person who posted the book.