I just finished watching the show today, and I'm more than impressed by the incredible work the creators have done. Every episode, every camera shot and every detail just works, Carnivale is a work of pure art. Only a handfull of shows can compare to this level of storytelling.
That being said, I'm actually semi-okay with the show ending after two seasons. The ending isn't bad. Many movies end with an open ending, and it's not necessarily a bad thing. Ofcourse I would have loved to see the continuation of the story, but that's just not likely any more.
I recommend every fan of Carnivale to read the backstory and mythology created by Daniel Knauf. Much of this can be read on Wikipedia, specifically on this page (general info on the show) and this one (on the mythology, a great read). It really adds to the show and can fill in some of the more confusing parts of the story.
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