I always believed the promotion ended on May 31st. I even made an effort during the last week of May to spend everything so I wouldn't lose any money.
Edit: Found a slick deals thread that said the promotion was supposed to be good for 2 months from the time of issue. I must have combined my $10/4 books with the Avis deal.
http://slickdeals.net/f/6890578-10-a...nt-credit-avis