The Face In The Frost, by John Bellairs. Mostly known for children's urban fantasy, Bellairs got started with this one, which despite having no specific content that wouldn't pass muster, is maybe a little too intense for the wee ones. It has some genuinely creepy, scary moments, and also some of the funniest I've ever read.

I played the main character of this in Drink Deep, and on the day I arrived at the hotel, Sean Butler came over and thanked me profusely for doing so, since it made him read the book.