It's a very important work. It brought together multiple storylines and characters in the DC universe. It explored complex themes like the nature of heroism and the consequences of power. It also redefined many characters' relationships and set the stage for new story developments.
DC Comics has a rich tapestry of dimension-related concepts. While not always explicitly defined as infinite, there are numerous instances where the multiverse and alternate realities suggest a vast and potentially infinite array of dimensions within the DC fictional framework.
There are quite a few main characters. Superman, for one, is always central in these big DC events. Batman with his detective skills and strategic mind also has a major part. Wonder Woman is there as a powerful and iconic female hero. Additionally, there are other heroes like The Flash who contribute to the story as they all face the challenges presented in the 'dc infinite crisis graphic novel'.
The main way it ruined DC Comics was that it threw the established order into chaos. It made it hard for new readers to jump in and for long-time fans to keep up. Plus, it seemed to sacrifice character development for the sake of a big event.