Knowing that Aetheria didn't really talk, Harley didn't expect her to say anything back to him. Sometimes actions spoke much, much louder than words and this was definitely the occasion for that. In the back of his mind, he did wonder what it would take to get her to make some kind of noise for him, a challenge almost. Something to definitely keep in mind for later, as it were.
Shifting to straddle his lap and rolling her hips into his? Yep, body language totally understood in this case. Harley leaned up into her, tilting his head a little so she could have better access to his ear, resulting in a few gasps of his own at that little tug from her teeth. Damn, she knew what she wanted - and Harley was so down with that. Sure, there was a chance they'd get caught, being as they were in the middle of a bookstore and all, but that just made it that much more intriguing for him. Brushing the hair back from her neck, Harley pressed soft kisses at the spot where her neck met her shoulders and then worked his way up, trying to figure out what made her tick.