This was marketed as the most exciting and best Joker story yet which actually hurts its chances to survive and be appreciated as its own story, really. The hype built around it will mislead readers who tend to have overblown expectations. So I suggest you adjust your expectations and don't expect this to be an instant classic or whatever it is being marketed as. It's not. But it's still a very enjoyable read. Like any avid Batman fan, finding out that the Joker will be returning in the New 52 line-up was instantly gratifying, especially since I consider him my most favorite Batman villain ever since Mark Hamill's version in Batman: The Animated Series. But DC did not make having the Joker back a walk-in-the-park either.
The entire point of the Joker's massively tormented (and, may I add, drawn out) return is to destroy the family that has made Batman weak because they humanized him. The Joker strongly believes that such relationships had reduced Batman into an ordinary and fallible man, and since the Joker's vanity is centered around the fact that he is unique and his nemesis is exactly as that too; and they are locked into an eternal battle of will and wits forever and ever (it's worth noting that there are lots of accidental homoerotic layers to the way the Joker pines over the Batman in Snyder's narrative framework), he thinks he's actually doing Batman a favor by eliminating his surrogate children and own son and heir. It makes perfect sense for the Joker to be this possessive and entitled to Batman. There's something vaguely pitiful about it too.
The last issue of this collection was personally satisfying if you focus on the echoing thematic dissonance between the Batman and the Joker as the dichotomy that they've always been: order and chaos; and placing that in a more humanistic context where they are more than just mere concepts but also people who are afraid to own up and face the flaws of their humanity and how much they have alienated and often damaged the few people who are important to them. There is that poignant scene where Batman threatens to reveal to the Joker his real identity and the Joker actually flats-out refuses. That for me was a significant look at how the Joker wants to operate; he desperately wants to cut himself off from any kind of humanity including his own, but there is loneliness to that so it would be comforting for him to know that Batman will do the same as well, considering the only lasting and meaningful connection he ever had was with the Dark Knight.
If you don't believe the hype created around this story and the entire crossover event then The Joker: Death of the Family will be an impressive accomplishment that is worth the purchase. Snyder wanted to reveal just how much Batman and the Joker are intrinsically tied to one another. This for me is also a major milestone among Batman and his children and I'm interested to see how it plays out for everyone concerned since they basically just endured another traumatic event that should re-define their relationships.