I'm getting the same impression of him across all three mediums so far. I still get the idea that he puts on the same composed, confident, rounded front he does in the anime/manga. The novel gives us a lot more reason to sympathize as nobody in the anime/manga had a single bad thought about him (besides Ozaki), but I thought it was implied in the anime/manga that he's actually always been quite unstable and fragile underneath, looking for his chance to blow. Later on he'll go around house to house to check out the deaths and we'll see him interact quite a bit more. Right now most of his scenes have been introspection, so it's easy for us to lose sight of how composed he is on the front. His introspection on his cutting, too, was brought about by Sunako commenting on his scar, when for years now the village stopped acknowledging it, at least in front of him, to the point where he'd all but forgotten it was visible to others.