More than anything I think this book made me realize how great the film is. Movies, especially dime-a-dozen crime dramas, rarely stick with me and this one really stuck with me. Both book and film explore the ways in which our pasts define us - internally and externally, for better or worse.
Both book and film are pretty bleak affairs, but I think the film adds a touch humanity that the novel lacks. I think the actresses (Laura Linney and Marcia Gay Harden) in particular added huge amount of dimension and believability to the female characters.
Still, it's an intensely readable novel and well worth reading for fans of the genre. I just think the film is a bit more effective. Many thanks to Lehane for providing the material and inspiration in the first place!