If diamondback turtles hold a certain fascination for you, you know everything there is to know about them, you talk about them all the time, and maybe you've embroidered one on your pillowcase. Fascination is an irresistible attraction.
Be careful to use the right preposition: you've got a fascination with handsome princes, but handsome princes hold a fascination for you. When you have a fascination, it's as if you're bewitched, and — what do you know? — the word goes back to the Latin fascinare, which means "cast a spell on."