I'm glad to see that DC Comics put out this second volume of "Showcase presents the Martian Manhunter" completing the series run as a back-up feature in "Detective Comics" (with Batman as the lead feature).
The "Martian Manhunter" series was then moved to "House of Mystery" comics that originally featured monster and sci-fi stories as a lead feature.
This was done when due to the poor and slumping sales of the Batman titles, Publisher Donanfeld reassigned the Batman titles from Editor Robert Canniger to Editor Julie Schwartz asking Schwartz to revamp the series and try to save it and do to it what he did with "The Flash" and "Green Lantern."
The Martian Manhunter" series, however, remained with Editor Robert Canniger who put it as lead feature in "House of Mystery" comics. A new series featuring "The Elongated Man" replaced "The Martian Manhunter" series in "Detective Comics."
J'on Jonzz, the Martian Manhunter, was also given a comical sidekick, an imp from the Fifth Dimension named Zook who was the color orange and had two antennae on this forehead. Another change made at this time was that the Martian Manhunter decides to stage the death of his alter ego, Police Detective John Jones. He needs to concentrate full time on this threat that is menacing the whole city. The Martian Manhunter and his partner Zook operated and lived is a hidden cave. They would enter the cave by walking through the caves walls.
The Martian Man hunter's comical sidekick, Zook, is later killed off.
"The Martian Manhunter" ran as the lead feature in "House of Mystery" for about two years and then was relegated to being a back-up feature again in "House of Mystery" with a new lead feature replacing it, "Dial H for Hero."
By the end of the 1960's, both superhero series were canceled, and the "House of Mystery" title was turned into a book dealing with stories of the occult and supernatural.
The Martian Manhunter who was also a member of "The Justice League of America" was also removed from the book as a member of the team.
Since 1955 when the Martian Manhunter first appeared in the pages of "Detective Comics," things had changed and much more about the planet Mars was known such as Mars has no life and cannot support human life on it. (Now we know that there does exist bacterial life on Mars, but no sentient life forms or civilizations).
By the late 1960's, the Martian Manhunter had become obsolete and irrelevant. Editor Julie Schwartz and writer Denny O'Neil decided to have the Martian Manhunter written out of the "Justice League of America."
J'on Jonzz, the Martian Manhunter, had repaired the scientist's teleported machine, which originally brought him to Earth years ago leaving him stranded on Earth. We now find that J'on Jonzz (the Martian Manhunter) was a political exile, exiled to the deserts of Mars by a dictator he spoke out against. That was when the Martian Manhunter had be caught in this scientist's teleported ray bringing him to Earth.
Back on Mars, the Martian Manhunter discovers that this ruthless dictator still in power plans to exert and strengthen his control over the people of Mars with the use of a weapon that goes beyond being a Weapon of Mass Destruction. This is a weapon that when set off can destroy the whole atmosphere of Mars leaving Mars a barren waste land with an atmosphere that can no longer support life.
The Martian Manhunter manages to teleport back to Earth and enlists the aid of his fellow Justice League members who go back to Mars with him. The ruthless dictator sets off the bomb in the end and Mars's atmosphere and civilization are laid waste. However, a rocket ship did manage to leave Mars containing a number of Martians did get away and went off to another planet in another solar system to colonize and star a new civilization. The Martian Manhunter decides to leave the Justice League to use a rocket ship left still functional to pursue and join the other Martians in the other world to help rebuild the Martian civilization.
These two volumes of "Showcase presents the Martian Manhunter are worth getting.
In a later "World's Finest Comics" issue done when Superman was the feature character in team-up stories, Superman goes to aid the Martian Manhuter on New Mars that orbits an orange sun. Under the rays of the orange sun, Superman only half their strength. This story is included in the first volume of compilation. Also included in the first volume is the first of the team-up series that ran in "The Brave and the Bold" comics. This was prior to Batman being cast as the featured character in the team-ups. The first team-up teams the Martian Manhunter with Green Arrow and Speedy.
As you know, teh Martian Manhunter was returned to the Justice League of America on Earth in the 1980's. They tried the Martian Manhunter in his own title later, but it was not successful.
I, myself, prefer the Martian Manhunter as he originally was in the 1960's, and these two volumes are a complete collection of the Martian Manhunter as he originally was.
These two volumes are good and fun reading.