This story starts from an author's mysterious disappearance, but while significant, this is secondary to the greater mystery of her account of her life, left for her heirs to read, which makes up the body of the book. A life full of dark magic, strange faeries and stupid adults who don't believe they exist.
Yes, we're in Unreliable Narrator territory again, something which is immediately obvious. But unlike many books using this device, this isn't intended as a dawning realisation to the reader. Instead, it prepares the ground for a bigger question: assuming she believes her account, why would she think that?
This is the start of a wild ride touching on some seriously dark themes, which would be huge spoilers if I expanded on them. Bruce's great strength here is in gesturing towards the answers, not telling you. Though she sometimes gives the reader a helping hand, there are major events which require you to interpret the narrative based on what we're told and what we know of reality. The result is a slowly unfolding tale of a deeply traumatic life, which still leaves room for speculation and uncertainty.
You Let Me In isn't a comfortable story. There's real darkness at its heart, way beyond the often creepy faerie folk. But nor is it generally graphic about the details. And the journey is absolutely worth it.