I cannot give Underground men an in depth review. The reason for this being, the fact that it's a single volume with a simplistic plot and bare bones characters. However, considering when Underground Men came out, this is all understandable.
The Mysterious Underground men is the first "Story Manga" by Osamu Tezuka before his rise to fame. It's literally the first manga to ever have a coherent storyline, as well as a tragic ending.
This is not, however, a masterpiece by any means, though that doesn't mean that it isn't worth a read. Underground Men Is a piece of history, and i would strongly recommend
it to anyone who considers themselves a fan of the medium.