I got the Shiki DVD, and it came with a some art that had Sunako standing in a library holding the Bible. I'll see if I can find it somewhere, but it's a really cool piece that's black and white and creepy-looking. All of the books are labeled too. I think there's a part in the manga where somebody says something like "the Shiki can resist the fear of holy items up to a point, which is how Sunako can hold and read the Bible"?

Were there holy objects in the tunnel? I thought they were just scared because the tunnel got too narrow to squeeze through.

I guess this is a good example of how the novel is interesting even if we've already seen the animanga, because there's still stuff left to find out! And even then, it would take way more than 2 novels to cover all of the possible plotholes, so there's still room to muse on it. I also like some things left up to the imagination; building headcanons is a whole journey in of itself.