Guarantee delivery

Why Amazon US got guarantee delivery but UK don't??

Guaranteed Release-Date Delivery (Saturday, July 21) of "Harry Potter and the Deathly Hallows"!

We will deliver Harry Potter and the Deathly Hallows on its Saturday, July 21 release date to eligible customers who pre-ordered from Amazon.com and chose standard, Two-Day, or One-Day shipping when placing their order. (Amazon Prime customers will receive it on the day of release at no additional charge. Learn more about joining Amazon Prime.) If you qualified for guaranteed Release-Date Delivery, in the unlikely event that you don't receive it on Saturday, July 21, we'll refund the cost of the book.

Most deliveries will be made by UPS or the U.S. Postal Service, either with your regular mail delivery or in a special, later delivery. All copies that qualified for Release-Date Delivery should be delivered by 7:00 p.m. in your time zone. If you have not yet received your copy, please wait until 7:00 p.m. on July 21 before contacting Customer Service.

I had ordered the book and stupidly put delivery address as Sam's office. The book will be released on 21 Jul (Sat), Sam not working on Sat!!!! Should I cancel my order and buy from shops on 21 Jul??? Or can I wait till 23 Jul (Mon) to read the book (where half the world already know what happen in the end)..... Errrr I don't think I can wait!!!