These two five issue miniseries essentially star the Phoenix force, and detail it's adventures in recent times. The first series was very popular, and "surprised many readers with its nuance and depth. The success led to a sequel featuring the continuing story of the Phoenix Force, X-Men: Phoenix - Warsong.
In the first series, the Shi'ar resurrect the dormant Phoenix Force prematurely and without a host, in hopes of destroying it. The Phoenix escapes to Earth where it resurrects Jean Grey and forcefully bonds with her again, despite Jean's pleas that it is "too early." Many hijinks ensue (I plagiarize well, not write well, and there's nothing worth taking except for the pure plot synopsis on wikipedia. follow the links below if you want spoilers).
The second series revolves around the Stepford Cuckoos and includes the team from Astonishing X-Men.
In the first issue of Warsong, the Phoenix Force attaches itself to the three remaining Stepford Cuckoos, amplifies their telepathic power, and gives them the power of telekinesis. With their newfound abilities, the girls overcome Emma Frost's psychic detention and resurrect their deceased sisters Esme and Sophie. Kid Omega also wakes, once again, from his stasis in Beast's lab. Cue hijinks. Try these out, they're better than you may think.