[quote name='WebScud']I just rented this and I couldn't really get in to it. It seemed right up my alley and I knew what to expect, but it still didn't grab me. Would reading the manga help at all?[/QUOTE]
Comic. Honest mistake, though.
I'd say yes, reading the series would help. But I'm a huge fan of the series, so of course I would say that.
What didn't grab you about it?
The movie roughly follows the arc of the comics, in that the first volume starts very slow and shows the relationship between Scott and Knives, with Ramona coming in roughly in the middle and the first fight scene right towards the end.
But from Vol. 2 onwards we get a lot more character development and backstory on all characters, most importantly on Scott and Ramona themselves (also Knives, Kim, and Envy).
So yeah, it rocks, and has way more time to flesh out the characters and their growth over the course of the story. Also note that the movie takes place over a few days, while the books take place over at least a few months.