Since both of these novels are by Atwood, I immediately began noticing similarities (and more often, differences) between them when I started reading Oryx and Crake. The two greatest similarities seem to be: the meandering narrative style, which is not my personal cup of tea but is certainly better than being dry and dull; and the overall dystopian viewpoints of the books.
Oryx and Crake
I just wanted to discuss the significance of Crake's decisions on how to modify humanity. It seems to me that, while his modifications were aimed at eliminating strife, the main result of his modifications were that he eliminated the part of humanity which causes strife, the main things he did was to eliminate the human capacity for progress. This emerges in his discussion with Jimmy about sex. Jimmy argues that by eliminating sexual frustration, he is eliminating art. I think this actually applies to nearly all human endeavors, including government, science, commerce, etc.
Crake constructs a new genetically engineered human race to live more "in harmony" with the earth and each other by removing the human propensity for violence, meat-eating, religion, etc. etc. Unfortunately, a lot of those are a more intrinsic to the human makeup than Crake originally guessed. The Crakers are alone, in a world they can no longer understand now that Crake has taken science away from them. The only connection they have with the old world is Snowman, so naturally they go to him for answers.
The author of an article I read for my term paper writes that SF and myths operate similarly. Both are a reflection of man's thirst for knowledge about his origins and his fate; SF is considered a more self-conscious form of myth-making. This is especially prevalent in Oryx & Crake, during those instances when the Children of Crake ask Snowman to tell them creation stories. Oryx and Crake are likened to Godlike beings: "Crake made the bones of the Children of Crake out of the coral on the beach, and then he made their flesh out of a mango.
While Snowman, as many people have pointed out, has a very grim life ahead of him, I found James Cole's life in 12 Monkeys considerably more disturbing. He experiences just about everything that could go wrong in a dystopian future: his life is manipulated by far more powerful people, he loses his grip on what is real and believes himself to be insane, and ultimately becomes a witness to his own death. As with many time-travelers, he is ultimately helpless in the past even though he has such extensive knowledge of it; Cole's story employs the Cassandra myth to find tragedy.
What ended up sticking out to me most while reading Oryx and Crake was how little good was attributed to the human race ("homo sapiens sapiens" [Atwood 99]). It was rather strange that despite hearing the story from a human's point of view, from Snowman's reflections on the past, the reader is presented with quite a terrible view of humanity.
It seems to me that Crake believes that in order for the human race to survive, it has to become essentially non-human. He is doing what he believes is necessary to save what he considers to be the best parts of humanity. Barring the methods by which he achieves it, I think that it is interesting to examine this motivation as it stands, outside of the context. Personally, I do not agree with what Crake considers to be the best parts of humanity, just as I don't agree with Butler's argument that the "hierarchical impulse" is entirely bad.
The central event for the novel Oryx in Crake is the advent of a mega-virus, named JUVE, which nearly completely obliterates the human population. All that remains after it sweeps the world are Snowman, aka Jimmy, and a bunch of "Crakes"...genetically engineered humans designed to live easily and peacefully. Oh, and apparently some other humans...but we don't find that out till the end (and book doesn't say much about them).
It's a common trope for fiction writers to hate science and technology. The idea that knowledge is a recipe for destruction is deeply rooted in the past, dating back to at least Prometheus' punishment for stealing fire from Mount Olympus. But the more blunt examples are those in the mad scientist category; the Frankensteins, the Jekkyl and Hydes, the Dr. Moreaus, the Lex Luthors, etc. By taking their pursuits of science to unethical extremes, these characters not only wreak havoc, but shame the entire concept of science.
What I found most captivating about Oryx and Crake was the total sense of isolation that saturates the book. The narrative helps in creating this sensation of loneliness because the reader is kept ignorant of the most recent events of Snowman's past up until the very last pages of the book. As we go along, we have the two separate periods of narration -- Jimmy's childhood and family issues, leading to meeting Crake and school, etc. and then Snowman's present.