Hush
Gotham Central (the arc with the Sniper, it takes place alongside Broken City
you can see a discarded newspaper with the Gotham Sniper headline in Broken City. Not sure if the trades out yet)
Broken City
Death and the Maidens
Superman/Batman: Public Enemies
As The Crow Flies
War Games (and I agree with the rest, as a whole its not worth the money. Its too long
interesting, sure, but worth the money youd spend on it? No chance)
Identity Crisis (which has had infinite reprints, so finding the individual issues may not be hard at all)
Identity Crisis is a mystery that involves the entire DCU and Batman plays a fairly large role. He doesnt have a lot of page-time, but the character is very important, especially near the end (and not for obvious reasons). The events of Identity Crisis affect Batman in a big way
it has repercussions that carry on to the OMAC Project mini thats going on now, which leads to the Infinite Crisis (which is DCs huge mega-event that will cross over to every single book and will have a large impact on those books) at the end of the year.