The link is not working properly on Scholastic's part. I had the same problem and sent them an e-mail from the link on the page. I told them how I tried to sign up and did not get a confirmation. I also asked how would I know if I got the book.
I received a response from Scholastic stating that they were having problems with the link and they asked that I send them an e-mail with the mailing information. They assured me that they would send the book.
Try this if all else fails! And thanks for posting this great freebie!