Miracleman can, in some ways, be seen as a parallel to Watchmen, in that it takes several of the same concepts but extrapolates them in a different direction. The responsibilities of being a godlike being, the superhuman as an object of terror rather than redemption, and whether superheroes should be seen as good or evil all pop up in Miracleman as in Watchmen.
Miracleman was Moore's reinvention of a comic from his youth, Marvelman. Due to issues with a certain comic book company, the name of the book was changed to Miracleman before making it over to the States. The story begins with a reprint of the original Miracleman series, featuring Miracleman himself, Young Miracleman, a younger version of Miracleman, and Kid Miracleman, an even younger doppelganger. Together they defeat some rather silly alien invaders in a rather silly way. While the Miracleman family is celebrating, the reader is treated to a quote from Nietzsche's Thus Spoke Zarathustra. Then things get really weird.
Mike Moran, Miracleman's alter ego, wakes up in 1983, having forgotten all about his previous life as Miracleman. He's a married, freelance reporter suffering from migraines, hounded by memories he can't quite bring into focus. During a terrorist attack at the opening of nuclear power plant, Moran turns, almost accidentally, into Miracleman. From that point on, the series becomes an exploration of mortality vs immortality, humanity vs godhood, and free will vs predetermination. It's heady stuff, sometimes too heady, but always surprising and entertaining.
Moore doesn't shy away from the sillier aspects of Mircleman's past, dealing with the Miracleman Family and their crazy adventures in a novel way. The reactions of Miracleman himself and of the rest of the family (once they're re-introduced) seem realistic, particularly Liz Moran, Miracleman's painfully human wife. I hesitate to say too much about the storyline because Chris is reading it and I don't want to spoil anything.
If I have any complaints about Miracleman, it's the way it ends. Alan Moore handpicked Neil Gaiman, of Sandman fame, to finish the storyline. Unfortunately, Eclipse comics went bankrupt 6 issues into Neil Gaiman's intended 12-issue run, and the rights to the character have been tied up in litigation ever since. I don't know if we'll ever see the end of Miracleman, but regardless, it's worth a read. A thought-provoking, mature comic book that work because of the format, not in spite of it.