In 1999, DC did a year-long story called No Man's Land. The rather ludicrous premise was that after Gotham City was hit by both a lethal disease outbreak and a massive earthquake, the entire city was essentially declared unsalvageable and no longer part of the U.S.A. Many got out, but some stayed. Including the residents of Arkham Asylum!
Batman has always had the best Rogues' Gallery, and I was familiar with most of the villains from the animated series, but reading NML was my first exposure to their comic counterparts (which showed me just how wrong the pre-Nolan movie portrayals were). The Penguin, Two-Face, and Joker figure most prominently, but a lot of others make appearances.
What's most interesting about No Man's Land is the portrayal of, basically, post-apocalyptic Gotham. Laws are meaningless, and resources are scarce. Bullets are worth more as currency than as weapons. Gangs form, and gang wars erupt. Some of it is a little over-the-top—would society really go to shit after two months? I suppose it's possible in a dire enough situation. And that's what the story is about, what happens in this dire sitution. The Gotham City Police Department tries to maintain order, and Jim Gordon has to continually face a moral dilemma and debate with one of his officers, Pettit, who believes that lethal force is the only language an anarchist people will listen to. People make unlikely alliances with villains who find that having control over people is worth taking care of them. As the first storyline proclaims, there's No Law and a New Order. But it's in these most trying times that you struggle to keep a grip on your own humanity and don't let yourself sink to the level of the petty criminals. Being a mainstream comic, it's not particularly subtle about this theme, but it does have its well-written moments.
And what of Batman? Gotham needs Batman like Batman needs Gotham, and Batman does his best to keep the city from destroying itself. He can't do it alone, of course. Oracle continues to gather information in a low-tech world, and Huntress tries to keep the peace any way she can. Robin and Nightwing get called in, as does Azrael, who I know very little about. And there's also the introduction of one of my favorite characters, Cassandra Cain. Our Heroes work together to fight crime! It's a good time.
Overall, No Man's Land is too sprawling a crossover event to really be great since the plot progression is kind of...intermittent. There are a couple major plotlines that continue throughout, but a lot of time is taken up by short stories that feature fun characters but don't add a whole lot to the Big Picture, exactly. And while there are great writers like Greg Rucka, Devin Grayson, Kelley Puckett, Chuck Dixon, and Paul Dini involved, there were also names I didn't recognize like Larry Hama, who provides an awful Mr. Freeze issue where Mr. Freeze and Batman fight while quipping. Batman does not quip! He's not SPIDER-MAN. The art style switches a lot too, from Alex Maleev's dark, noir style to Damion Scott's more comic-book, animated-series style. I don't remember disliking much of the art, thankfully.
But it does have a lot of great moments, especially for the villains, who really get to be showcased. A couple of them get to be truly terrifying. (And Harley Quinn gets integrated into the DCU! She is not really terrifying.) There's a lot of good material for Jim Gordon as well, plus his rocky relationship with Batman. Renee Montoya features as well, and I still need to read Gotham Central. It's a good story if you like your Batman caped and cowled (there's very little Bruce), protecting his city. And even though Gotham eventually has to be restored by the end, NOTHING WILL EVER BE THE SAME!