This is one of the most useful Greasemonkey scripts I have ever installed.
From the description:
Often Amazon’s non-US sites have less detail for books than Amazon.com does. Also, Amazon.com seems to have more books that you can look inside before buying, and the book viewer is better than on (some) international sites. This script turns the ISBN-10 and -13 numbers into a links that search the US site for that ISBN number, which will usually take you to the page for the book on the US site (though note that not all books in all countries will be sold on Amazon.com, or not with the same ISBN, but many will). This means that you can quickly click through to the US site to check out a book in more detail, before deciding to buy it (click back to the non-US website first, obviously).
I find it particularly useful because amazon.com tends to have many more reviews for each book than amazon.co.uk (unless the book is British).
