Really, these two should just get it over with and get married...
SPOILER ALERT -- nothing huge though since the whole story is less about "Is the Joker really going to bite the dust?" (ch-yeah, right) than the overall hamster wheel that is the Batman/Joker relationship.
In "Killing Joke" Batman says to Joker "I've been thinking about you, me. We're going to kill each other aren't we?"
In "Death in The Family" Bruce Wayne thinks to himself, "we've been linked together so long, neither of us truly understanding the bond"
And now comes another chapter, with a twist. After all he's done--crippled Batgirl, killed Jason Todd (one of them, anyway) -- Batman finds himself in the position of having to actually save the monsters' life. He's accused of distributing poison stamps, which translates into premeditated murder, and you can't plead insanity on that (let's remember of course that this is the DC universe law book here, and that the Joker's done dozens of things that could just as easily be construed that way. But then, he'd have been fried in the chair years ago, and what fun would a world without Joker be?)
Against everyone else's wishes -- Gordon, Alfred, the cops, -- Batman solves the murder and gets Jokey off. Reason would dictate that he just wait until the Joker's executed and THEN find the real killer, but as he says to Gordon "It doesn't work that way." Once again, Batman is the iconoclast, going his own way. This only rates three stars because there's not much that has a lasting impact on the reader, unlike KILLING JOKE and DEATH/FAMILY.
There is one poignant sequence featuring Oracle (nee Batgirl) when Batman actually has the gall to ask her to help him in his case. This draws on the suggestion that Joker and Bats really are intertwined in some twisted binary string. Joker is madness and chaos. Batman is rational and intellectual. Yet, Batman uses his rational thinking to preserve the existence of the Joker's madness. To some, Batman's madness may be worse, since it comes cloaked in friendly attire. (Well, you know what I mean...)
Of course, this does go back to the point of KILLING JOKE. Batman will not--cannot--sacrifice his ideals on the altar of the Joker's madness, no matter what. (Ok, so he left him to die in Death in The Family, but he went a little insane after Robin's death. He would later save Joker's life AGAIN in both Hitman #3 and the Legends of the Dark Knight arc "The Demon Laughs")
A good book, get it for [$$] or under if you can.