I really like Amy's stories. They are always intriguing and fast paced, and never boring.
This, more than most has a great sense of creeping dread, a sort-of "mystery-box" build-up, before revealing the answers to many questions and forcing the heroine (Sister June) to overcome her crippling shyness and come into her own as an individual who controls her own fate.
I'd say this is probably Amy's best book for a long time (not that the others are bad, but this is a step up).
And yes, I get that some people say her writing style isn't great, but then neither is Dan Brown's or JK Rowling's. I found the story compelling enough to overlook the way characters seem to "stammer" or "mutter" every other line of dialogue, and to be perfectly honest, that was the only real weakness I found in an otherwise enthralling tale.
Recommended reading for certain.