Some people think Multiversity is confusing apparently?
Multiversity is about superheroes from different worlds being summoned to team up and defeat villains (The Gentry) that are threatening the entire multiverse one earth at a time by corrupting and destroying them. Because Nix Uotan (the Multiversal Guardian/Last Monitor) was defeated.
The bit with the comic books in the story is how the universes communicate with each other, as in the comics on say Earth 10 are stories from Earth 20.
And each issue of the series between Multiveristy #1 and 2 features a story on a different earth.