The Crater is not just one story, but a collection of 17 different stories (with the last one being called "The Crater") of supernatural mystery.
I've read in some articles that it was made during an experimental period in Tezuka's career. He was transitioning from his adventurous and chldish-focused stories (like Lost World, Astro Boy, Kimba the White Lion etc) to write more mature content. So The Crater is an experimental work; he was trying new stuff and made a collection of short stories to see how it would go. I think this fact is the answer to my opinion on each chapter: some of them were pretty good; some others chapters, on the other hand, were so confusing that I just stared at the last page wondering what the heck was that.
If you enjoy "Twilight Zone" or something of the sort, you're definitely going to enjoy reading this manga.
The art is bad, but you have to keep in mind that it was drawn in the late 60s, so that was the stardard way to draw during those times.