X-Men: The Dark Phoenix Saga

When sent on a mission to contact a young mutant Katherine Pryde; Cyclops, Wolverine, Storm and Xavier are ambushed by the minions of a the mysterious and exclusive Hellfire club bent on world domination. Lead by a mysterious villain who holds a telepathic connection to Jean Grey's ancestry, Hellfire's inner circle now has the power to destroy the X-Men once and for all. What ensues is a gripping tale of betrayal, identity and sacrifice as the Phoenix seeks to harness the full potential of Jean Grey's mutant abilities. 

In the vast and complex history of X-Men,the story line regarding Jean Grey's alter ego Phoenix is one of the most famous and shaped many relationships between key characters on an emotive level. Though this story was re-imagined in episodes of the 90s animated series and was also central to the third X-Men movie directed by Brett Ratner, Claremont's original is by far the superior telling of Jean Grey's transformation into the Phoenix.

If you have any interest in the X-Men franchise but are overwhelmed by the amount of publications, this stand alone book is a good place to start. Collecting the Dark Phoenix Saga from multiple issues, the story plays out in a clear linear fashion with only a few annoying re-cap moments and linear notes which were included to help readers keep up when reading the original run.