Isn't guaranteed to always work, but in general it'll work for a short term soluction if you don't need anything to last too long. It -might- work longer, but I know some people have had issues with it.
You can shorten any B&N link by changing barnesandnoble to bn, so www.barnesandnoble.com becomes www.bn.com . This will work on any B&N link, so if you're linking to a particular book page, you can do this, too.
And, you can remove the title of the book from the url as well. For a random example, I grabbed this book off the front page of BN.com ( http://www.barnesandnoble.com/w/america-again-stephen-colbert/1110788777?ean=9780446583978 )
So you can remove the "america-again-stephen-colbert/" part. And shorten barnesandnoble to bn.
So you get www.bn.com/w/1110788777?ean=9780446583978 which should go to the same page as http://www.barnesandnoble.com/w/america-again-stephen-colbert/1110788777?ean=9780446583978
Granted, it's not the shortest ever, but it is shorter. No idea if it helps or not.
People have had issues with this sometimes, though, where after awhile the shortened link doesn't work correctly.
Is the place you're wanting to put this on allow simple HTML? If so, you can just do a link thing with like... <a href="link here">Book Name</a>, too. That's probably a preferred way of doing it, but I realize you can't do this everywhere.