Um... it's awful and don't watch it. Mark Hamill is great but, seriously, don't watch it.
Anything I could say has already been said by others. So I'll just link to a few reviews that I recommend.
* Batman the Killing Joke Animated Movie Review by Reaf
* The Killing Joke Movie Is a Disaster, Right Down To Its Comic-Con Panel
* The Killing Joke Movie Is Stuck in the Worst Parts of the Past
I could post more, but you get the idea. It wasn't well done. The only one that gave it any effort was Mark Hamill, who has been wanting to do this for years. Even Kevin Conroy sounded like he was phoning it in.
So yeah, to quote Brad Jones: "It's not the worst Batman movie I've seen this year." But this was still a pile of garbage that included a festering, cracked, molding kitchen sink.
Grade: D-. The only reason it's not a full F is because of Mark Hamill.