I'd agree with the positive reviews, and say that yes, its the Joker origin that seems the most 'right' to me.
I personally really like the style of skewed expressionistic artwork (I'm sick of the tepid 90s style which seems to dominate most comics).
Good story, great dialogue and narration, and I like the way Batman and Jokers origins are entwined. The characterisation of the Joker was just perfect.
Pre-accident Jack was just as interesting a character as the Joker, which is a pleasant suprise since most stories can't seem to deal with that aspect of his character very well.
I don't buy the 'tragic' backstory for a character like Joker (since just about every other Bat-villian has a tragedy... why can't they just be *******s?).
So yeah, you've bought a great HC.