Fledgling, by Octavia Butler

This is an amnesia story, where the protagonist finds herself in a situation she doesn't understand and has to work out what happened; and where she turns out, along the way, to be a person of remarkable power and importance. As such, it zips along. I find the amnesia both too convenient (it's carefully targeted to avoid causing any problems that aren't useful to the plot) and really effective. Adding to the paciness, the protagonist (who doesn't initially know her own name) shares with other Butler protagonists I've read a clarity and force of mind and motive: around her, things will get done, and they'll get done well.

It's fun to start amnesia stories not knowing any more than the character does, but also in this case maybe not. Plot description commences here: it's vampires. Or something like them. The protagonist quickly finds that she wants to drink human blood, and that when she does so, the person she drinks from becomes emotionally bound to her, extremely interested in her welfare, and extremely suggestible. Being fed upon is a sexually charged pleasure. This starts out uncomfortable because the protagonist appears to be about eleven years old, but quickly does a partial flip and becomes uncomfortable in the opposite direction as well: the protagonist has to reckon with the control she's achieved before even knowing what kind of being she is, and with the circumstances that deprived her of that knowledge.

( Late-book spoilers on how this power dynamic shakes out )