The first volume was a limited series which collected stories from the Thomas/Adams/Palmer run on X-Men (originally published in 1969).

The second volume was an unlimited series and reprinted stories from the post–Giant-Size X-Men era (originally published in 1975).

The second volume was launched in 1986, reprinting the "All-New, All-Different" era of X-Men.

The first 27 issues have various edits and new pages added to tie in with then-current continuity.

The series also included new covers and frontispieces produced by artists such as Art Adams (issues #1-16, 18-23), Steve Lightle (#30-42, 44-52), Mike Mignola (#57-70), and Adam Hughes (issues #71-79).