Batman: The Killing Joke
The Killing Joke is a graphic novel, written by Alan Moore and illustrated by Brian Bolland. The story features how the Joker came to be in flashbacks, and how the Joker plans to turn James Gordon insane. The book is regarded as one of the best Batman comics ever, and has had numerous praise from reviewers and people with a connection in the Batman world, such as Tim Burton and Tim Sale.
The Joker escapes from Arkham Asylum again, and purhcases an abandoned and deadly circus, with intent to decend James Gordon into madness. Upon taking him from his home after crippling his daughter, the Joker leads Gordon into his fair - in which, he terrorizes him to prove that all it takes for someone to go insane, is one bad day...