This is the 2856th most frequent Turkish word.
gizem
"Secret, mystery, enigma."
Here, 'gizemli' means 'mysterious', an adjective derived from 'gizem', depicting the quality of having mystery.
Gizemli bir adam ormanda dolaşıyor.
A mysterious man is wandering in the forest.
In this sentence, 'gizem' is used as a noun meaning 'mystery', describing an intriguing and unknown aspect of the book's ending.
Bu kitabın sonu gerçek bir gizemdi.
The ending of this book was a true mystery.
Here, 'gizemlerini' refers to 'its mysteries', indicating possessions of mystery by the house and used as a plural form to imply multiple unknown aspects.