Ed Brubaker is perhaps the best writer currently working in comics, so his arrival on "Uncanny X-Men" in 2006 was highly anticipated. The initial result, a twelve-issue story arc set in space called 'The Rise and Fall of the Shi'ar Empire', had a mixed reception (I enjoyed it, personally, although it wasn't up there with his best work). He had initially planned to depart afterward to make room for Mark Millar, but after Millar's linewide project fell apart in the planning stages, he stayed on, resulting in this story arc, leading into the excellent "Messiah CompleX" crossover.
The end of the previous arc left Havok, Polaris, and Marvel Girl in space with the Starjammers, and another castmember, Darwin, does not appear here; carrying over from the previous team are Professor X, Nightcrawler, stranded Starjammer Hepzibah, and Warpath, the character Brubaker pulled from obscurity and made a fan-favourite (his greatest success with the X-Men to date). They are joined by the former Morlock Caliban and longtime stalwart Storm, who had been absent from the team for a year or so after the ludicrous marriage with the Black Panther designed to boost that book's sales. The mission in question is twofold: Storm leads most the team to investigate the actions of a band of Morlocks led by the evil Masque, while Professor X and Nightcrawler set out in search of Magneto, missing since the confusing events of "New Avengers #20". The second story is rather abortive, featuring only a brief appearance by big M that serves to set up his post-"Messiah CompleX" status quo. The first story is more interesting, delving into the fallout of M-Day (when all but a handful of mutants lost their powers) among the Morlock community; religious cults have developed around a series of prophecies by a deceased Morlock, and Masque knows how to read them, and believes he sees a future where mutants still rule the world. He's willing to go to extreme lengths to bring it about. The story is a bit slow, but it's interesting, and it sets up future stories for the X-Men.
On art, Salvador Larocca returns to the X-Men yet again, brings the hyper-real style he's been working with on "Newuniversal", and it looks pretty good, although it's maybe not the best kind of stuff for a superhero title (I did enjoy his Patrick Stewart-style Professor X).