Watchmen
Alan Moore and Dave Gibbons' comic WATCHMEN contains a lot of Moore's magical preoccupations in seminal form, although it was written almost a decade before he bacame a practicing magician.
There's the chaos aspect (which would have been the central theme of Big Numbers), wherein all the different threads of the story are commenting upon one another. There's the simultaneity of time (a notion which reappears as 'four-space' in From Hell) from the viewpoint of a man locked inside a nuclear reactor primed to explode; and the disjointed quantum consciousness that results. The sheer sureness and concreteness of the anchoring visuals: everyday objects become recurring motifs, so clear and steadfast that they take on a strange new significance.
Moore would go on to more and, arguably, better work, but never again anything as perfect and complete as WATCHMEN.