http://ebooksdirect.dianeduane.com/collections/frontpage/products/young-wizards-new-millennium-editions-9-volume-box-set
and enter the code LIVEJOURNAL at the end of checkout (after you've approved payment of the full price on PayPal - it goes back to a page on Diane Duane's site for entering offer codes)
Offer ends Tuesday night 11:59PM Hawai'ian time.
60% off offer applies to all her other books too.