Kinnikuman is, as I understand it, an important pillar for the development of the shōnen nekketsu battle manga genre, bridging the tropes of pro wrestling action and storytelling with the traditions of Japanese tokusatsu heroes to establish a new breed of action manga. The thing is, no one gives a shit about this manga in America because all we got was a dub of the sequel's anime which was butchered by the infamous 4kids, as well as a curiously uncensored release of that manga, functionally making it so Americans only really know of Kinnikuman's son, and the rest of the new generation of Chōjin.
Well, it's hard to really talk much about Kinnikuman with this first volume anyway, since at this point it's basically just a silly parody of Ultraman. Kinnikuman is a loser of a superhero, powered by eating garlic, and capable of doing a couple variations on the Specium Ray, but mostly ineffective as a fighter. Roughly the first two-thirds of this volume is focused on Kinnikuman being a loser, though he starts (kind of inexplicably) getting better later on, shortly after a brief arc with Meat impersonating Kinnikuman to save the world from kaiju while our hero sleeps at night. If I'm not mistaken, we're getting to the Chōjin Olympics by Volume 3, so I guess Kinnikuman will improve his skills over the course of the next volume? Anyway, we also see Terryman briefly, who'll be pretty important when we get into the chōjin wrestling that will make up the vast majority of the franchise.