Witchcraft: a Primer
Ectoplasm, Cauldrons, and Graves, Oh My!
Tarot
The Geography of Black Lake
and twelve volumes of An Anthology of Banned Books.

You could read one of them, though your mission to escape this house could be put in peril if something were to catch you here. Then you notice one of the books next to the gap seems a bit... off...
You press the book into the shelf, and the whole shelf starts rotating! Cool, a hidden staircase!

You hear the door behind you lock, and trying to open it proves impossible. Your only option for a hasty exit seems to be leaving through the secret passageway.