** spoiler alert **
A pretty involving book, from beginning to end. Lehane's writing is lean, crisp and very readable. The three main characters are very distinct, even though Sean does lose a bit of his "voice" going from boy (in the prologue) to man (as a cop in the mystery). I figured out the two main "mysteries" solutions earlier than I would have liked, which gave the last third of the book a bit of a predictable nature, but overall I enjoyed the book. A lot darker than I expected, more raw and gritty than I would have been led to believe, based on the overwhelmingly positive reactions I got from (mostly) older women who had read it and saw me with the book throughout the week.
SPOLIER ALERT! If you haven't read the book or seen the movie yet, you may not want to go on with this review.
I love that Jimmy starts off a brutal, wicked guy and, try as he might, never quite becomes redeemable or even that particularly likeable. Even with the compassion built-in with the death of his daughter (a great device that Lehane uses to all kinds of wonderful effect, both story-wise and character-wise), Jimmy still can't escape his own evil nature and he slinks back to join the slime he came from by the end.
Dave is a terrific character, although the whole "Boy" thing isn't explored as much as I thought it could have, but his demise is played out very nicely. For a few pages, there's the idea that he may not get whacked, but then the brutal nature of the antagonist comes shining through and Dave feeds Mystic River with his body and soul.
Depressing stuff, but the best scene in the book has to be the tense, violence-in-the-air conversation between Jimmy and father-in-law Savage at his daughter's wake. Great stuff there. The wrap-up scene at the parade is also nicely played, leaving all kinds of doors open for another book.