Many creative liberties were taken from Frank Miller's original comic, somewhat unusually when considering its acclaim. Also, the animation had far more Japanese influence than it did Frank Miller's.
Clearly, rather than please the fans of the original book - it tries to maintain the audience of the recent film trilogy. For example, there's an early scene in which Batman uses 'fear gas' on Harvey Dent's henchmen in which they suffer nightmarish hallucinations. These hallucinations don't appear in the original…