X-Men The Dark Phoenix Saga written by Chris Claremont, co-plotted and penciled by John Byrne, inked by Terry Austin
The X-Men are returning from another adventure when Jean Grey experiences yet another seeming time slip where she inhabits an ancestor of hers from the 18th century. The 1700s Jean Grey is head-over-heals in love with Jason Wyngarde. Unbeknownst to her there's a modern-day Jason Wyngarde who is a member of the inner circle of the Hellfire Club. The overall club is populated by the rich and powerful of America. The inner circle is a bunch of mutants with world-domination ambitions. They want to bring other mutants into the fold, especially Jean Grey. Her telekinetic and telepathic powers recently went off the chart when she became the Phoenix. When the X-Men get back to headquarters, Professor X sends them to check on two new mutants detected by Cerebro (Kitty Pryde in Chicago and Dazzler in New York City). The Hellfire Club has secretly hacked into Cerebro so they are after the two new mutants and they know all the powers of the X-Men. A hard fight is in store.
This book is a far ranging and focuses on Jean Grey's psychological turmoil. At first she can't figure out what's going on with the time slips; the earlier Grey is more dangerous and cruel. But that's just a side of her personality she keeps under wraps. Keeping that undercover is harder and harder as her powers grow and the corrupting influence of Wyngarde deepens.
The story is also loaded with lots of action which occasionally go over the top, especially at the end. The drama goes to eleven, but in a satisfying way.