I remember seeing later books from the Gor series on the bookshelves when I was a young G.I. on weekend passes, and thought them intriguing, but wasn't into fantasy at that point in my life. After I did begin to appreciate fantasy, I decided to start the series from #1 and fully expected it to be like John Carter of Mars, only perhaps better.
There are similarities between this and Burroughs' John Carter of Mars, but it's certainly not better, or even as good.
The adventure takes place on the "counter earth"--a planet in an orbit that keeps it perfectly opposite the earth and therefore hidden by the sun. A mysterious power structure called the priest-kings keep weapons technology stuck in the middle ages, while allowing other tech to advance even beyond present-day earth's. Norman rambles on at length explaining his world-building, which really tested my patience (but I would have forgiven this if the story had been better)--he obviously thought out those parts extensively.
The big weak elements are character and plot. Tarl Cabot is a naive, gullible adolescent rube in the body of an action hero. There's a romantic subplot, of sorts, with a princess of an enemy city, but what they see in each other is a mystery to me. She despises him as a clueless wimp from the beginning, and as he proves himself even more of a clueless wimp, she falls in love with him. And he her. I guess because she was the first female character Norman tried to develop in this book, and he was too lazy to introduce another one. So far as that goes, I suppose he's following in the footsteps of other pulp writers.
Tarl Cabot is romantic and grandiose in his sterling chivalry. His thick-headed foolishness is a plot device to get him into the obligatory perilous pitfalls, and dumb luck is the device which gets him out.
In the climactic swordfight against Gor's greatest swordsman, Tarl is overmatched and just barely escaping a mortal wound, until Norman got bored or just decided to wrap things up. Then, without explanation, Tarl magically becomes the superior swordsman and wins the fight. I see this in Hollywood movies all the time, so I admit I was sick of it even before reading this scene.
After reading some of the other reviews, I think I'll give the series 1 more try, starting with Assassin of Gor. This idea had much potential, but the execution fell short.