This is a great story about Gotham City and it's residents. I saw that it's that rather than a great Batman story because, well, Batman's barely in it. Batman, along with his more famous enemies such as Joker and Two-Face, are more-or-less restricted to cameo appearances, while the plot mainly focuses on a corrupt businessman named Warren White and a few other villains that are either obscure foes from earlier on in Batman's career (such as Magpie) or new villains invented for this series (such as Humpty-Dumpty.)
If you've ever seen One Flew Over the Cuckoo's Nest, the plot is basically a Batman version of that. Warren White is on trial for cooking the books of his business, and argues for the insanity plea, figuring that life at an asylum would be nicer than life at prison. He fails to account for the fact that he's in Gotham City, and that being sent to a mental ward means being sent to Arkham Asylum. Now White has to figure out how to survive in the same place as psychos such as Joker, Two-Face, and Killer Croc.
The book has some scenes of strong violence and disturbing images, along with a subplot dealing with the occult, so if you're opposed to any of that stuff, skip it. Batman's barely present in the story at all, so skip it if you wanted to see him, too.