Where it all started:
Fantastic Four Annual #2 (Doom origin)
Additional inserts:
Blade #2 and Dominic Fortune #4-6
Fantastic Four v.4 #9
Before the Fantastic Four: Reed Richards #1-3
Invaders 32-33 & Marvel Universe 2
Books of Doom #1
Books of Doom #2
Books of Doom #3
Books of Doom #4
Books of Doom #5
Books of Doom #6
Fantastic Four #268,278,279
Fantastic Four vs X-Men
Triumph And Torment
What If? Secret Wars (not in continuity, but has some interesting details)