Superman Fights Generic Villain With Incredible Powers
'The Challenge of Terra-Man!' is like a lot of other stories that ran in Superman in the decades of the 60s, 70s and 80s - basically a villain (not one of Superman's regulars) shows up, possessing incredible powers of science and/or magic, and proceeds to whoop the pants out of superman for several pages before the Man of Might manages to incapacitate him (and he goes on the shelf for a few years).
This time it's an Old-West type villain, with a winged horse, and a six shooter full of gimmicky high tech bullets. To make matters worse, Superman is at a disadvantage due to the hitherto before unexplained fits of pain and depression that occur to every Kryptonian once every six years (didn't you know that?).
It's not a bad issue. It's not a good issue. It is a typical issue of it's era. Whether or not you'd want to read it, probably depends upon how you feel about typical mid-70s Superman stories.
Bonus points if you can spot a cameo by two popular (at the time) TV characters.