This is H.L. Humes' previously mentioned second and final novel, Men Die. It is much shorter (less than 200 pages) and was published the following year in 1959 by Random House to similar acclaim. While the title is maybe a little blunt, Men Die is much more daring and technically-inventive than The Underground City, in addition to being far more compact. It centers around an explosion in an American munitions depot just before the outbreak of World War II in the Caribbean. The Underground City is a better book in my opinion, but Men Die has its own merit and is also the last piece of writing from H.L. Humes. The back and front cover art is some of the finest I've come across—the current reprint only has the front title in black being that it's a paperback.