Julia Quinn, It's in His Kiss

Miss Bridgerton,” he said, “the devil himself couldn’t scare you.”
She forced her eyes to meet his. “That’s not a compliment, is it?”
He lifted her hand to his lips, brushing a feather-light kiss across her knuckles. “You’ll have to figure that out for yourself,” he murmured.
To all who observed, he was the soul of propriety, but Hyacinth caught the daring gleam in his eye, and she felt the breath leave her body as tingles of electricity rushed across her skin. Her lips parted, but she had nothing to say, not a single word. There was nothing but air, and even that seemed in short supply.
And then he straightened as if nothing had happened and said, “Do let me know what you decide.”
She just stared at him.
“About the compliment,” he added. “I am sure you will wish to let me know how I feel about you.”
Her mouth fell open.
He smiled. Broadly. “Speechless, even. I’m to be commended.”
“You—”
“No. No,” he said, lifting one hand in the air and pointing toward her as if what he really wanted to do was place his finger on her lips and shush her. “Don’t ruin it. The moment is too rare.

Romantic Quotes And Sayings by Julia Quinn, It's in His Kiss