THIS IS NOT THE CROSSOVER TO GET YOU INTO DC
we had another forum regular who tried getting into DC with IC and he hated it, because it's so complicated and features a cast of thousands, and is just built upon too much stuff that came before. Really, they've been planning this for a long time now, so there's countless stories that lead into it.
Here's a great list of DC books from the past few years that you should read, preferably in chronological order (the ones with dashes represent optional, but excellent, stories):
Green Arrow vol 1: Quiver
-Green Arrow vol 2: Sounds of Violence
-Green Arrow vol 3: The Archers Quest
-Batman: Hush
-Teen Titans vol 1: A Kids Game (reintroduces the group, they're important later)
Identity Crisis (MUST Read)
Green Lantern: Rebirth
Countdown to Infinite Crisis (someone help me, what trade has this issue?)
(the following are the DC "Countdown to Infinite Crisis" miniseries. They are all completely optional, but it wouldn't hurt to read one or two for set-up. They each deal with a different side of the DCU as Infinite Crisis approaches. IMO, none were really that great.
-Villains United (deals with DC villains)
-Day of Vengeace (deals with DC Magic)
-The Omac Project (Deals with Batman chiefly)
-Rann/Thanagar War (Deals with DC Space)
-Sacrifice (deals with Superman and Wonder Woman)
Infinite Crisis (should be in trade in a few months, certainly by the time you get through the above list)
Really, IMO, if you want an absolutely awesome book to get you more into DC, check out DC: The New Frontier. Also, Green Arrow vol 1, 2, and 3 I would recommend to ANYONE regardless of what they're trying to get into, because they are just some magnificent stories.