I have the first edition of The Sky: Art of Final Fantasy, which was limited to 1000 and was signed by Amano. It comes with a few goodies compared to the new slipcase edition: it comes in a box set, includes the book "All About Yoshitaka Amano", a flipbook, an acetate print, postcards as well as a card signed by Amano. I realize it's an extremely rare and valuable item, although I'm considering reselling it since I'm not actually collecting artbooks, and I think that an actual collector would probably enjoy it more than I do.
It's opened, although I never actually read it. I just took a look at the contents and quickly flipped through them though everything is still as new and the box set was carefully preverved (in a smoke-free, pet-free environment).
I'm not set on a fixed price, so if you're interested, please make an offer! :)