This comic is so good it feels like I'm cheating by writing about it. Honestly, my critiques are so minor compared to how many things I feel are not just done right, but perfectly, it's hard to start. Hence me rambling on in this self-conscious manner.
Astonishing, cribbing the name from one of the Age of Apocalypse books, picks up where Grant Morrison's New X-Men left off; Jean's dead (for a while this time), Emma and Scott are a power couple running the school while Xavier helps in Genosha, and the X-Men in general are scattered and confused. With that, Cyclops essentially decides that since someone will lay claim to the X-Men name, the mutant community is best served by having the highest quality X-Men possible, and assembles the team himself.
For reasons of having a balanced skill set and good public image (discarding the all-new, all-leather costumes of the Morrison era, except as casual wear), he brings together himself, Emma, Hank McCoy, Kitty Pryde, and Wolverine. Later on, Colossus has his shot at returning to life, joining the team and resuming his relationship with Kitty.
The arcs more or less break down as the X-Men dealing with a malicious alien attempting to wipe out mutantkind with a "cure" and violence, the sentient A.I. of the danger room, the apparent return of the Hellfire Club's Inner Circle, and a resolution of the issues with anti-mutant aliens (the latter has yet to be collected, but is almost finished).
When it comes to the writing, I would be sorely tempted to call this my perfect image of the X-Men. Everyone gets their due (even Scott), but nobody overshadows the rest of the team (not even Wolverine). The dialogue is as good as we've come to expect from Whedon, being interesting and witty while remaining in-character for each of the distinct personalities. The plotting is solid, with the only low point being the second storyline, "Danger," which shoehorns Whedon's ideas about A.I. in a disjointed story. Arcs aside, Astonishing's two year run reads as one long story with self-contained issues in six-issue arcs. Therefore, don't look to this for and single-issue reading; give yourself some time to read at least an arc at a time.
John Cassiday's art is detailed, active, and expressive. Action has punch, and you'll never confuse characters as everyone has their own unique features. However, he may have some sort of eyelash fetish, seeing as he exaggerates their portrayal on everyone's face. Even the aliens and robots. Regardless, his use of form and color leave one with a "real people in a comic setting" impression that compliments Whedon's writing perfectly.
The bottom line about this series is: "If you've ever liked any of these characters or even the concept of the X-Men, read it, dummy." Also, if you've always felt that nobody ever "got it" when you've tried to read X-Men, give Whedon a chance to win you over. He probably will.
Thus far, the storylines collected are titled "Gifted," "Dangerous," "Torn," and "Unstoppable" (again, yet to be collected). Taking over after Whedon is Warren Ellis (who apparently writes 75% of Marvel between him and Bendis). I'm greatly saddened to see this run end, but if Whedon feels he's finished I won't argue. Besides, maybe with Ellis Astonishing can go back to being monthly instead of every other month.
Yeah, I'm so hooked that I buy every single and the trades. Try it, and see if you blame me.