Since DC just released the first trailer for the upcoming animated adaptation of this classic novel, I thought I would dig into the history of this famous, as well as controversal, Batman story.
Alan Moore wrote the story because he wanted to come up with his own version of the Joker’s backstory and psychology.  He wrote the Joker as a tragic character, who became who he is because of “one bad day”. He wanted to show a similarity between Batman and the Joker.
Alan Moore later said he was not a fan of the book in a 2000 interview. “I don’t think it’s a very good book. It’s not saying anything very interesting.” He elaborated on that in 2003
The Killing Joke is a story about Batman and the Joker; it isn’t about anything that you’re ever going to encounter in real life, because Batman and the Joker are not like any human beings that have ever lived. So there’s no important human information being imparted ... Yeah, it was something that I thought was clumsy, misjudged and had no real human importance. It was just about a couple of licensed DC characters that didn’t really relate to the real world in any way.
In a 2006 interview with Wizard magazine, he discussed being critical of the decision to paralyze Barbara Gordon 
“I asked DC if they had any problem with me crippling Barbara Gordon - who was Batgirl at the time - and if I remember, I spoke to Len Wein, who was our editor on the project ... [He] said, ‘Yeah, okay, cripple the bitch.’ It was probably one of the areas where they should’ve reined me in, but they didn’t.”
Emphasis is mine because I think it needs to be there.
EDIT: mgwtfllbbqb found an AMA Len Wein did for I09 back in 2013 where he discussed the “Cripple the bitch” quote.
This scene brought a lot of well-deserved criticism from the feminist community. Author Brian Cronin noted that “[many] readers felt the violence towards Barbara Gordon was too much, and even Moore, in retrospect, has expressed his displeasure with how the story turned out.” . Author Sharon Packer wrote “Anyone who feels that feminist critics overreacted to [Gordon’s] accident is advised to consult the source material ... Moore’s The Killing Joke is sadistic to the core. It shows Gordon stripped and mutilated, with before, during, and after photos of the attack displayed before her bound and gagged father, the police commissioner. She is more than merely disabled.”
The book explores Allen Moore’s assertion that psychologically, “Batman and the Joker are mirror images of each other”. He did this by exploring the relationship between the two, and how they react to their tragic days. The theme of the story is how each man responds to just one bad day, and where they go from there. Critic Geoff Klock explained that “both Batman and the Joker are creations of a random and tragic ‘one bad day.’ Batman spends his life forging meaning from the random tragedy, whereas the Joker reflects the absurdity of “life, and all its random injustice.”[ The story uses the Joker as an unreliable narrator who admits his own uncertainty to the memories of the event that caused his transformation. He says, “Sometimes I remember it one way, sometimes another ... If I’m going to have a past, I prefer it to be multiple choice!”
Christopher Nolan has said that this story was an influence for the Joker who appears in 2008’s The Dark Knight. We see this in the number of different stories told about how the Joker got his scars. Heath Ledger said that he was given a copy of the graphic novel as a reference. 
Artist Brian Bolland credited his version of the Joker from having seen the movie The Man Who Laughs. DC Managing Editor Dick Giordano’s invitation led to Bolland working with Alan Moore to come up with a background for the Joker. He recalled, “I thought about it in terms of who’s my favorite writer at the moment, what hero I would really love to do, and which villain? I basically came up with Alan, Batman and the Joker.” The fate of Barbara Gordon had to be approved by editor Lee Wein. 
The production of the 48 page prestige format one shot took a lot of time. Both Moore and Bolland were known for their time consuming meticulous work and both had just finished 12 issue maxiseries that had seen delays . Eventually Alan had fallen out of favor with DC but continued to do the work for Brian’s sake. “by the time Alan had finished Watchmen he had fallen out with DC to a certain extent ... [i]n the end, he only continued to do Killing Joke as a favour to me.”  The original editor Len Wein left and was replaced by Dennis O’Neil who Bolland described as a “very hands-off sort of guy,” who Bolland recalls only have one conversation about the book with..
I know it has issues but Killing Joke is one of my favorite Batman stories. It was one of the first I bought when I got into comics and I can’t wait to see how the DCAU team adapts it for animation. I hope you enjoyed learning some of what went on behind the scenes of this classic book, and I will see you all next week for another Midweek Trivia,
1. Will Brooker, Batman Unmasked: Analyzing a Cultural Icon (Bloomsbury Academic September 18, 2001) pp. 268-272.ISBN 978-0826413437.
2. Kavanagh, Barry (October 17, 2000). “The Alan Moore Interview: The Killing Joke and Brought to Light”. Blather.net.
8. Geoff Klock, How to Read Superhero Comics and Why (New York: Continuum, 2002) 52-53. ISBN 0-8264-1419-2.
11. Bolland, “The 1980's - The Killing Joke” in The Art of Brian Bolland, pp. 195–197