Instead of going into a big long explanation of what Age of X is, lets just start things off with this:
At least they are being fairly upfront about it. Age of X: Alpha does exactly what the creators intended. It sets you down in the middle of an alternate world with little explanation. We are introduced to different versions of familiar characters. For example, Cyclops is known as Basilisk in this world. Here we have a character that was used, against his will, as an executioner of mutants.
The issue ends with the X-Men going off to battle. Well, not really the X-Men as they don’t call themselves anything. In fact they barley even function as a team. In the next chapter of this story, we see this battle, and its end result. A mutant is killed and Legacy, known in 616 as Rogue, is called to ‘save’ her. Basically, Legacy absorbs the memories of mutants before their death. Cannonball refers to her as ‘The Reaper’ a nickname which Legacy states she hates. (Rogue is not Rogue! Rogue is Legacy! But Legacy hates the nickname Reaper! Grrrrr! So don't call her Rogue! Or Reaper! Or Anna Marie!) Its also interesting to see Cannonball give orders to Basilisk. Especially since in New Mutants Cyclops is the one Cannonball looks up to and takes orders from. Frankly, I’ve always liked Cannonball so anytime he gets a moment to shine is cool in my book.
As for other well known characters, Wolverine has no powers and acts as a bartender. I’m serious. As someone who can’t stand Wolverine this amuses me to no end. We follow Legacy as she is out alone, dealing with the newly absorbed memories when Kitty Pryde shows up. This sets off a chain of events that causes Legacy to break into the holding cell of Fortress X to unravel the mystery that Kitty brought with her. Legacy eventually meets Professor Xavier and battles Danger. At the end of chapter 2 she is now a fugitive.
As the story progresses it seems that Magneto is in on the whole thing. He arranged Kitty’s escape and capture. He rescues Xavier as Gambit and Legacy penetrate a secret room in Fortress X. A room Magneto has no memory of building. In that room is a box. A box that contains the universe.
It turns out this world, this Age of X, is simply a fantasy created by a mental antibody in Legion's mind. When the New Mutants subdued Legion he was brought to Utopia where Dr. Nemesis began working on his fragile mind. He began to simply eliminate the multiple personalities, but Legions mind fought back.
While this is an interesting premise I’m not sure about the execution. I guess it just comes down to personal taste and I’m just not a big fan of imaginary tales (usually). Age of X was designed to invoke memories of a better alternate universe story, Age of Apocalypse. You have Magneto leading a rag tag group of mutants. Our once familiar characters are screwed up, mentally and physically and have strange, unexpected relationships. Though I admit, Storm and Namor does kinda make sense to me.
As this reality begins to unravel and the X-Men are restored to the 616 universe we see there will be some fallout from this event. Emma is not happy that Cyclops was with another woman while in the Age of X. Storm and Namor exchange an awkward glance. I’m glad there will be repercussions from this event. I feel, though, that this is an event that could have benefited from three or four more chapters. We really only get to know these alternate versions for a brief time before their world unravels.
Ultimately, Age of X pales in comparison to Age of Apocalypse. We are only given a brief taste of this alternate reality and form little attachment to these characters. It also doesn't help things that the characters do very little aside from fight the military and argue with each other. Legacy, Legion, and Basilisk are the most developed characters. Wolverine has his moments, but thankfully he is almost an afterthought.