You could say that Frank Millers highly acclaimed what if Batman story is an essential early read for anyone wishing to get into Batman comics. It contains arguably one of the most important Batman/Joker storylines ever printed; its one of the first to flat out say one cannot exist without the other. Basically The Dark Knight Returns surmises that, after The Joker murdered Jason Todd in the previously discussed A Death In The Family, Batman hung up his cape and cowl for good, only to be called back into active service when a new and terrifying gang seizes Gotham. It also surmises that, without Batman, The Joker falls into a catatonic state and doesnt move or even speak for a number of years. However, when The Dark Knight finally returns the terrible beast awakens within the Man Who Laughs and he too returns, worse than ever; hence, theyre two sides of the same coin. Millers Joker is strangely cold compared to how Ive seen him portrayed in other books, strangely humanised, while the psychopathy that drives him is, as always, never far from the surface. Its a grittier, scarier and wholly understated take on the character and one which Miller himself has enjoyed masses of praise for since. If you ask me, this is almost a direct parallel to how Ledger approaches his performance. Its difficult not to link Ledgers bristling Clown Prince to Millers presentation of the character in The Dark Knight Returns; Id even argue that Nolan had this whole book in mind while crafting his own grittier, more realistic cinematic take on the Batman universe.