You sit down on the chair.
At first, it simply rocks back and forth.
After a short time, you start to feel very uneasy and unsafe, and you quickly get off of it.
Looking back, the chair seems ordinary, aside from the rocking.
You guess sitting in it again will have the same result.

So, you can either examine the book in the candlelight,
or take the candle and go back to the hallway.