I have been reading my way through an event which changed the world of the X-Men in many ways. The Age of Apocalypse (AOA) while set in an alternative universe spilt over into the regular Marvel universe, and proved to be very popular with fans.
AOA cast many familiar characters in unfamiliar roles. Professor X is killed by his son and America is invaded by Apocalypse who starts culling humans. Magneto wants to fulfill the dream of peace that his good friend Professor X started and groups together a resistence called the X-Men. He also marries Rogue and they have a child together.
Alex and Scott Summers are servants of Apocalypse having been raised by Mr Sinister who also controls the Dark Beast a scientist who will go to any lengths to design new super soldiers.
Sabertooth is a noble member of the X-Men, while Logan is a wild warrior who loses a hand to Cyclops' energy beam.
Fans of the X-Men will enjoy the twisted version of the world they are familiar with, and they will notice that certain characters have crossed over into the Marvel Universe. These include X-Man (AOA's version of Cable), Dark Beast who replaced Beast and caused all sorts of problems and Holocaust Apocalypse's son.