The Uncanny X-Men - Facsimile Edition #135

Plot

The Phoenix Saga shifts into high gear as Jean Grey wields the godlike power of Dark Phoenix! Try as they might to reach the teammate they love, the X-Men are mere playthings to this elemental angel of death - and soon Dark Phoenix leaves them behind to embrace her destiny in the stars. But the fateful cosmic choice she makes will irrevocably change the course not only of Jean Grey's life, but also those of all the X-Men - and the scope of the entire Marvel Universe!

It's one of the all-time great Marvel comic books, boldly re-presented in its original form, ads and all!

Reprinting X-MEN (1963) #135.