Certainly few people had ever interested him so much as Dorian Gray, and yet the lad’s mad adoration of some one else caused him not the slightest pang of annoyance or jealousy. He was pleased by it. It made him a more interesting study.
– Oscar Wilde
The Picture of Dorian Gray, Chapter 4. Aristocratic puppet master Lord Henry wants to manipulate and control Dorian. The young lad’s "mad adoration" for actress Sibyl Vane doesn’t in the slightest make Henry jealous, but rather makes him an even more interesting challenge for Henry. But Dorian seems to be more of a guinea pig for him than just an "interesting study," as Henry puts it.