"The Nemesis from Terra" is the title of a science-fiction novel written by Leigh Brackett, published as an Ace Double in 1961. It was originally published under the title "Shadow Over Mars", in 1944. I do not know how much rewriting or editing was done between the two editions. The Ace Double edition had "Collision Course" by Robert Silverberg as its other side. Additionally, the book was apparently later published as a Tor Double, with the other side being written by Leigh Bracket's husband, Edmond Hamilton.
As a peek behind the scenes, my process of reading Ace Doubles varies. Due to their short, and accessible nature, it is possible to pick one up and dive right in. At times I read one in an evening. Sometimes, either because I have other things to do, or because a story is a bit more complicated, I might pick it up, read a few pages, and then put it down. There is a noema and noesis to reading a text, and sometimes I enjoy the process of reading as a process, without much understanding of what I am reading. This book took me a bit longer to get through, and I had trouble keeping up with the plot. There is a man named Rick Urquhart, and he lives on Mars and in a noir turn, the owners of a mining firm kidnap him and he leads a revolt. He is hunted down by various forces, escape and finds some mini-Martians underground, who crucify him, and he falls in love with an angel-winged Martian girl, and also with an earth girl, and after being double-crossed by his fellow revolutionaries, he returns to Mars, where he fights a battle against the villain in a polar arctic circle, where beings called "The Thinkers" lie in suspended animation, and at the end of the story, Rick Urquhart has to leave Mars for exile. Oh, and also, at one point in the book, he actually says: "If that ain't just like a dame".
So while reading this book, I thought it was a confusing mess, although I certainly thought there was a lot of ideas present here.
Researching this book afterwards made me reevaluate my inability to follow the plot. Leigh Brackett was the screenwriter, along with a guy named William Faulkner, of a movie called "The Big Sleep", considered one of the best noir movies ever made. And several decades later, she was the screenwriter, along with a guy named George Lucas, of a movie called "The Empire Strikes Back", considered one of the best science-fiction movies ever made. (She wrote the first draft of "The Empire Strikes Back" shortly before her death, and many of her ideas were altered, but she was still instrumental in the development of the film). So while it might be unfair to other writers who I didn't extend the same benefit of the doubt, but I decided afterwards that me not following the story was my fault, not the writer's fault. And indeed, I can imagine that working as a screenwriter might have been responsible for some of what was hard to follow: visual representation of characterization and setting might have made parts of the plot more comprehensible.
So I have determined that this one is a classic---even if I didn't get it while reading it.