There are so many possible X-Men futures (let alone Marvel ones, as a whole) that this story has a lot of competition. Sadly, I think it fails. I'm usually a fan of Grant Morrison's writing, but in this book it's way below his usual standards. There are lots of parts in this collection which really need to be expanded on and explored to create a fuller story, but Morrison seems to be contented with going for the "cool" factor (like Image did in the early 90s - all looks and no substance), which leaves you feeling that this collection should have been a couple of issues longer to give it and the characters some fleshing out and depth. The art, however, is nice; though it's hardly Silvestri at his best.
This collection is no Days of Future Past. It's not even an Age of Apocalypse, as far as alternate timelines go. Jean Grey would be turning over in her grave - because she's dead...AGAIN!.