This is a scene from third book, Bartimaeus is summoned by Kitty, they try to clear things about each other to each other in their own ways and Bartimaeus suggests Kitty to be the first to make the big step she talks about. To trust him and step out of her pentacle.

"Why don't you step out of the pentacle? Give the power to me for a change." – I tempted her, while watching eagerly, waiting for at least a finger to cross the chalk lines. I would've been on her faster than a cat onto mouse.

She doubted. Pale fingers reached for the outer line and hesitated. And as I wanted to sneer at her empty words, girl jumped up and out of her pentacle. I must say, for one second we switched sides complete. For one second – I hesitated. But then I got my old self back. Jumped up and rammed her back onto the floor, pressing her shoulders down with my Ptolemy-hands, knees bend around her on floor by each side. I did consider turning myself into something greater than slim form of Ptolemy, but what does a body mean? Be it a bug or be it a lion, I was same great Bartimaeus of Uruk, N'Gorso the… You know the rest, pick one, add 'noble' or 'great' and we're done.

Her eyes were closed tight in fear, face shaped into a mask of soon-to-come pain. She did not move for few long seconds. Neither did I. Why? Beats me.

But the second she opened her eyes I understood that I was wrong. It wasn't fear at all. It was just this tiny fear of getting hit in the head when falling on the floor, and a hit of something else. We stared at each other for few very long seconds. I can't explain this to you, but I could, and I always could, practically see the gears in her head spin faster and faster as she thought. The difference between now and then, when we were in the old library and she thought of escaping, is that this time she did not glance at the door. Instead, she glanced at the loincloth I wore.

"Did I hurt you badly, Bartimaeus?"

"You can't hurt me badly, girl, I'm a very powerful djinni, do not forget that."

"Good. I won't."

She moved quicker than a fox, when she grabbed the bone-white cloth, trying to remove it without making it too obvious why. I do not know why thou, as it was still obvious. Or would have been after few seconds.

Kitty feared for djinni to move away, to stop her when he understood her intensions. So she tore the loincloth of his tanned slim body and wrapped her hands around his waist. All her senses spoke of him being a human, yet her mind knew it all too well. The creature she craved was a demon with thousands of years behind him. And when she felt a warm palm on her breast, she also understood all the experience he must have too.

Bartimaeus indeed knew far too well how to behave. His hands slipped beneath her hips, raising her just a little onto his own laps. Then one hand moved to lean by her side and face her eye to eye. Or in this case – lips to lips. Girl arched her back in pleasure, trying to be even closer. The pain of pleasure made her dizzy and she couldn't keep the moans in. She wasn't even sure what she stroked or where her hands were at all. She just felt his skin all around and his hot and hard shaft inside of her, as the wicked center of the world around which she had to spin without any sense of where she is and if she IS at all. Her mind was lost.

And it took her quite some time to regain it after all was done. Dawn slipped through the window in the room. Her body felt limp and dead-weak. Her breath now calm lifted her breasts easily. A button in her shirt, which was now far under her, pressed against her skin painfully, but it was too hard to get back moving. And only when she saw the slim Egyptian figure above her again, she regained some of herself back. Kitty blushed and cought, trying to cover it. And herself, which wasn't easy. Body coordination seemed a hard task at the moment as her limbs still felt shivering and weak.

"Oh there's no need to blush, Kitty Jones. Not after that. Can you get your pretty bottom into the pentacle?"

"You wish to leave?"

"Well, you either keep me entertained here, or let me go and regain my strength in the Other Place. And from the way you're trying to lift yourself up, it seems that you should do the second option too. Just – here."

"Can I… Summon you again? After a while naturally."

"Even if I am not under you will right now, our positions hardly change after I leave. You will summon me if you will wish and I can't do anything about it. Better you than Mandrake, I can give you that…"

And as Kitty pronounced the last syllables of djinns release, he winked at her with a mischievous smile on his face and disappeared, leaving her with his own thought. Till the next time, Kitty Jones.