This was the first “direct market” issue, which means it was sold only at specialty comic book stores. The story itself is a one-off involving a mutated rat. Very creepy, and, for its time, very adult. It signaled a new era for comic books: Gone would be the drug store spinning rack, and the future would be in higher prices, better quality paper and, for the most part, better quality comic books.
However, it also heralded the beginning of speculators: People who would buy comics for investments rather than pleasure. Eventually, this would lead to variant covers; dealers overbuying #1 issues and keeping a hidden stock in the back, which they’d pull out a few weeks later and sell at inflated prices; and Todd MacFarlane basically being a dick and saying “people will buy anything I draw so give me my own Spider-Man title and let me cram tons of shit into it and prove what idiots my fans are.”
But I get ahead of myself.
Moon Knight was good to the direct market, and the direct market was good to Moon Knight: Without this niche market, the book would have been cancelled.