A non-spoilery review from reddit:
https://www.reddit.com/r/movies/comments/4u150u/the_killing_joke_just_opened_in_my_city_heres_a/
"In general I enjoyed the movie, it was decent and had a good time watching it. The film seems divided into two very different parts, so much that it feels like two completely separate movies. The first half is more devoted to building context for characters and laying the foundation for the themes that the film will adress. This first half is also the weakest part of the movie because at times it is pretty slow and the events are not really interesting or cautivating, also there are some weird scenes between Batman and Batgirl.
The second half, which is darker than the first, is where things go bat**** insane and is where most of the content of the graphic novel is adapted. Regarding the sequence of events and dialogue I'll say they're about 90% accurate to the source material. Kevin Conroy and Mark Hamill really shine from this point on, specially Hamill because he brought an even darker tone to his voice acting for this movie, at times it's ****ing scary. This second half is miles ahead more enjoyable than the first half, mainly because it's centered around Batman and the Joker without adding unnecessary subplots.
Now, where the movie falls short is in the animation. There's an overuse of CGI backgrounds and other elements, which at times look unfinished and done at the last minute. The 2D animation, at various points, looks quite sloppy. There is little attention to detail making the environment look very flat and the characters stale. Also, the transitions between scenes and flashbacks are clumsy, whereas the transitions in the graphic novel where smooth and thematic to the story. What also surprised me was that for an R rated Batman movie it wasn't as dark as it could've and should've been, I think this is mainly due to the animation making things look bland, the visuals in the movie didn't delivered that insane and dark atmosphere that was needed for the story, and couldn't match the dark tone from the voice acting.
To conclude:
The Best: The superb voice acting by Kevin Conroy and Mark Hamill. Watching Batman and the Joker voiced by these two guys is worth the movie experience alone.
The Worst: The animation. DC needs to spend more money and hire some Studio Ghibli level animators."