Three Shadows embodies the fear parents have of trying, but ultimately being unable to protect their child from threat. The parents respond very differently to the perceived threat to their child. The way they operate differently in the world is a marked contrast.
As Josh said at the meeting, there isn't a lot of dialogue and the graphic novel conveys much of the story in the illustrations.
I would say this is an excellent contender for Thumbs Up 2009. My only concern is the level of teen appeal. It is for an older reader (through adult). Some readers may object to the nakedness which is not meant to be titillating, but demonstrates the (au) natural openness of family. The discussion that could arise from a deep reading of Three Shadows has the potential to be quite profound and insightful.