I just attempted to post a long review of The Killing Joke, and it's stuck trying to preview. So I've probably lost it, and it's not worth retyping.
Verdict: don't bother. It's unbelievably poorly-done, unless you liked the graphic novel and start watching at the 28 minute mark.
EDIT: Oh, wait, I was able to recover it without headache. Here you go:
No, no, no. They completely screwed the pooch with Killing Joke. How the hell do you do that? By mashing a bad episode of Batman The Animated Adventures to a short graphic novel adaptation and making a movie out of it. If you want to watch it as an animated version of TKJ, just start watching around the 28 minute mark. And from there it's a pretty fair adaptation, though I hated the way they translated the very ending...for the record, Kevin Conroy could possibly pull off a creepier Joker than Mark Hamill.
Now, granted, the original book wasn't the most enjoyable story, but it was important as the first attempt at giving the Joker an origin and attempting to humanize him to a degree, and later being the springboard for Barbara Gordon becoming Oracle. At its heart it's a tale of the Joker. What they did was try to make it a Batgirl story, but they really, really failed at it.
The first 28 minutes are about her being pursued by a crook who's infatuated with her, and when Batman tells her to back off she takes it as him being domineering. Which he is, and they wind up having angry sex on a building. So after he pushes her off the case and keeps her at arm's length afterwards she leaps headlong into finding the bad guy, finds out that Batman was right that she'd put herself into it too far, and walks away from crime-fighting in the end.
Now, aside from Batgirl screwing Batman--which is totally at odds with all comic continuity (this is not Animated Universe where such a relationship was hinted in Batman Beyond)--this would be perfectly fine if TKJ was a Batgirl story or if she had any meaningful involvement in the rest of the movie aside from what Joker does to her in an effort to drive the Commissioner insane. But it's completely tacked on and artificial, and when you see the fidelity to the source material in the rest of the show it just blows my mind that they thought it was a good idea in any way, shape, or form. Batgirl is now more or less a jilted lover of a guy who in the comics was far more of a father figure than ever a paramour. And that's pretty much what you're left with...unless you count the mid-credit scene where they suddenly remembered, "oh, right, we need to wrap up Batgirl's part in this movie," and they show her with her Oracle alias. Which is totally unexplained to the viewer unfamiliar with the character.
END SPOILERS