Okay, so this should really be considered a 4.5 star review. Deaver is an amazing writer, skilled in the ways of writing truly engrossing mysteries. He gives the reader enough to figure out the mystery, but he doesn't really give the whole mystery away until the last word of the book. Kudos to Deaver for that. Deaver has become my favorite fiction writer, bar none. He's just that good.
But that said, the reason this review should be considered a 4.5 star review rather than a 5 star review is because of a couple of problems with this text. This story was much more engrossing than his previous Rhyme book, The Stone Monkey (a great book, nonetheless). The villain in this book is downright spooky and fantastically evil. The murders are grotesque yet not quite over the top. And the character development, especially the Rhyme/Sachs dynamic, is good for Deaver.
It should be said, however, that if you've never read a Deaver book before, this shouldn't be your starting point. And also don't read his books for tremendous insight into the human character. His books are plot driven, and, as a result, characters often develop too quickly in time to be wholly believable. But if you can suspend your disbelief, and it's usually easy to do that with Deaver, then you should have no problems enjoying his books. Scratch that. Reverse it. You should LOVE his books if you get past that point.
No plot spoilers here, but my biggest problem with the book is his big twist. His GOTCHA moment. While the twist made sense, I didn't feel that the twist had been properly developed to be truly believable. It didn't detract from my interest, though, and I enjoyed the hours I spend living in Deaver's fantasy that is The Vanished Man. As soon as I finished, I gave it to a friend to read.
Finally, if you've never read Deaver before, the following books should be your starting point, in my mind:
1) Read the Rhyme series in order (Bone Collector, Coffin Dancer, Empty Chair, Stone Monkey, Vanished Man).
2) Read non-Rhyme books: my favorites are The Blue Nowhere, The Devil's Teardrop, A Maiden's Grave.