The Ancient and the Amber by Amy Yorke

With just three months until the king razes her new home to build a coal mine, Alison Lennox and her friends travel to the isolated campus of Winwold College, a beautiful old castle nestled deep in the mountains of Loegria. There, they meet eccentric Professor Mircalla Marin and her bumbling graduate student Leo, the only people who can help them fix their solar generator in time to save the town.
But when a massive storm cuts the campus off from the outside world, strange things begin to happen.
Whispers come from ancient texts. Doors close on their own.
And, in the darkened hallways, something is lurking just beyond sight.
When a student goes missing, Alison and friends must race to find out what’s happening to the college before it claims another victim–and before time runs out to save Herot’s Hollow.