A dark premise in combination with the Dark Knight makes for an excellent story of struggle against the power of darkness. The premise is that a massive earthquake has struck Gotham City and the federal government has declared the city uninhabitable. The residents were ordered to evacuate and then the city was sealed off from the rest of the country. Those that remained are engaged in a ruthless battle for survival with criminal gangs carving out territory. A few sections are controlled by people (such as Police Commissioner Gordon) that genuinely want to make things better, but most are controlled by those with a lust for power. Some of the bosses are the traditional adversaries of Batman such as the Penguin, Two-Face and Mr. Freeze.
Within this mix are Batman in one of his darkest forms as well as Robin and a second generation Batgirl. Superman flies into town with the goal to aid in the recovery and meets Batman, who tells him to get lost. Puzzled, Superman ignores him and flies off to do some good. With the help of an engineer, they are able to get a power generating station back online, but this creates even more problems. Faced with an "I told you so", Superman flies off and leaves the solutions to Batman.
Commissioner Gordon and Batman are not allies; in fact Gordon is showing signs of the same mental instability that plagues Batman. Gordon is so opposed to Batman that he is willing to make a temporary alliance with criminal gangs in order to capture territory from another.
Post-apocalyptic battles to recover civilization have been a staple in literature and the movies for decades, sometimes they are well done and sometimes they are ridiculous. While there are some questionable premises in this story, it is easy to ignore them as Batman and his entourage struggle to restore some modicum of civilization to the ravaged streets. Great artwork and dialog about people under great stress.