Talky and Gimmicky
So we've already had the Puppet Master cliché the issue before last. What cliché haven't we had yet? The old switching bodies routine - you know, where the villain switches bodies with one of the heroes?
Well, that's pretty much what we have here, with Dr. Doom switching bodies with Mr. Fantastic. Then his plan to get rid of the rest of the Four is needlessly complex, the story is full of both plot holes and really bad characterization - the characters both act out of character, with unconscious knowledge/instincts, or with just plain stupidity through most of the later parts of the story.
The inclusion of Stan Lee and Jack Kirby in their own comic sounds far more interesting than it actually is.
And, worst of all, the issue is all talk - lots and lots of meaningless blather - as if there wasn't enough time for Jack to pencil the thing, so they decided to maximize word balloons and have Artie Simek fill the panels.
This issue will probably try the attention of even dyed-in-the-wool Silver Age fans.