If you don't already know, the other reviews will fill you in on the Watchmen's story and it's significance to the comic medium. I'm here to tell you about this edition of the book, which is basically an oversized version of the long out of print Graphitti Designs hardcover version complete with all of that edition's exclusive extras (which is fantastic since that out of print volume goes for major bucks on Ebay when it does rarely surface). Until now, that Graphitti Designs edition was the one to own...This tops it due to it's oversized pages and superior quality printing.
Want to see how this story was originally about about Captain Atom, Blue Beetle, and the Question (along with other Charlton characters) and how it changed to what it is? There is a very indepth look at the original proposal included here.
Want to see early Gibbon's art? it's here. How about rarely seen teaser strips published long before the first issue? Again included. Alan Moore's script samples? You got it.
Bottom line, I can't think of anything that could possibly be done or included that would make a superior edition to this.