Finished My Sister Rosa by Justine Larbalestier.
Che and his sister Rosa have just moved to New York with their parents. It should be exciting but all Che wants is to move back home to Sydney. Actually, no. He wants to move home, to be able to spar (he boxes but his parents won’t let him actually fight or spar), to get a girlfriend and, most importantly, to keep Rosa under control. Because something is wrong with Rosa.
This is a deeply unsettling book. It’s not like The Good Son or any other cheesy horror film. Rosa is old enough to know that she’s not like other people and she’s smart enough to be able to fake it (it helps that she’s really adorable). And she promises not to kill anyone…unless she knows she’ll get away with it. Che thinks it’s a joke. (I was a lot more skeptical.)
If you’re in the mood for something creepy, give this one a try. Recommended.