Medusa, with her crazy stretching prehensile hair, first appeared as a villain in Fantastic Four. Bigger things awaited, as she was eventually revealed to be an Inhuman and one of the good guys. What's an Inhuman? The result of an ancient attempt by the alien Kree Empire to mess with human genetics in the interest of... well, as presented here, simply because. Later retcons would make the Inhumans a weapons experiment, an idea that persisted on the TV show Agents of S.H.I.E.L.D. this season. But here, the Kree are basically interested in the science of genetic engineering for its own sake,
So are born the Inhumans, who form a highly advanced society of super-powered beings while humanity still lives in caves. They'd eventually hide from the rest of humanity until they encountered the Fantastic Four and gradually came out of that hiding.
Ideas and characters come bursting out of Jack Kirby here, most of them still in use by Marvel today in comics and other media. Some issues of Fantastic Four have been carved up so that just the Inhumans sequences are reprinted. That's a good idea in this case -- in several cases, the Inhumans material is a B-plot that only gets a couple of pages in a comic.
Kirby's storytelling is action-packed and occasionally poignant. Two of the great under-rated Lee/Kirby superhero battles appear here, as the Fantastic Four battles two of the Kree, first the long-slumbering Sentry and then the 'public executioner,' Ronan the Accuser. Ronan got burned off in somewhat altered form in the Guardians of the Galaxy movie. Too bad -- he's a much more interesting character when he's not Cuckoo.
If one owns a collected Lee/Kirby Fantastic Four in some form, this volume isn't necessary (though it also includes Inhumans stories from the back pages of Thor). But even then, this is a pretty good way to encounter the Inhumans, who are sorta like mutants except that they're not. And as always with the Fantastic Four under Lee and Kirby's direction, there's a pleasing and almost unique blend of low comedy, soap opera, action, and cosmic moments. Highly recommended.