TL;DR: "The Killing Joke" is a well executed, if disjointed retelling of the classic Batman story. Controversy is overblown. Will not be everyone's cup of tea.
Finally had a chance to watch the new animated adaptation of "The Killing Joke". I think it was very well executed. Aside from the less psychedelic color palette, some of these shots are right out of the panel. The ambiguity the the comic is famous for feels both less and more uncertain here, but to explain how would ruin it for anyone unfamiliar.
The voice cast is stellar all across the board. Kevin Conroy will always be my Batman. Pairing him with talent like Tara Strong and Ray Wise is like mana from above. Mark Hamill turns in a masterful performance as the Joker, but then he always does. Though this is a somewhat more subdued version of the clown prince than people unfamiliar with the book may expect.
One word of warning to the uninitiated, "The Killing Joke" is not an upbeat or "fun" Batman story. If you're mainly in it for action or laughs, look elsewhere. The tone is serious, cynical, and cruel.
There's been some controversy about the new material added to the story to make the release feature-length. I will say that the new material feels very disjointed from the contents of the book. That's not to say that it's bad, just that it doesn't feel connected in any way to the latter half of the film. That said, I did enjoy having an animated story that focuses on Batgirl.
Some are irritated at the implication of a romantic relationship between Bruce and Barbara, and I personally think that's an over-simplification. You've likely heard that the story somehow weakens Barbara as a character by "Anti-Bechdel-izing" her. But I think that is not only a simplified interpretation, but is missing the point. Thematically, I think the film is playing off of Bruce's long and tenuous relationship with each of his proteges. He has to maintain a stoic distance to protect them and teach them, but at the same time he does care, and that leads to pain and conflict.
In the case of Batgirl, it's undeniable that she idolizes him bordering on obsessive in some stories and interpretations of the character. And seeing her and a role-model walk the line between the various roles they've setup makes for some interesting tension. Seeing Barbara try to make sense of her feelings for Bruce and their source while also rebelling against his well-intentioned control through the lens of youth is a side of the character you don't often see and I personally appreciate it's exploration. In the same manner that I (as a huge Sherlock Holmes fan) applaud when a media doesn't shy away from the negative aspects of Holmes' personality as a drug addict and semi-psychopath.
I also personally think that being overly upset about the perceived injection of "man-trubs" is a bit odd given the level of actual tragedy that befalls Barbara in this book. This doesn't mean anyone's feelings about this take on the character are invalid, it's just not the hill I'd plant my flag on if I'm trying to make a point about portrayals of feminist icons in media.
All in all, I'd recommend it to any Batman fans, but would caution the weak of heart. Definitely not for young children.