It is not that Angel's attempting to sneak up on Lev in the library. But he is, by his nature, rather quiet. That is, he's not breathing, and his footsteps trend light and careful, and the Rabbi might not realize they're not alone until they're not alone and there's someone at the shelf next to them. Or something, depending on your view of such matters.

"New in town?" Okay, he doesn't breathe (nor blink, apparently), but he speaks, in a thunderstorm rumble of a voice, curious.