Born Wicked (Cahill Witch Chronicles #1) by Jessica Spotswood.*
Cate Cahill was fourteen when her mother died, making her promise to take care of her two younger sisters, Tess and Maura. Which would be tough enough if they were ordinary, but the three Cahill girls are witches.
With her father mostly away on business, Cate has kept a tight rein on Tess and Maura. But now that Cate is sixteen, Maura fifteen, and Tess twelve, their interfering neighbour Mrs. Corbett has talked their father into hiring a governess for them.
Yes, the Cahill girls are witches. In the alternate America of the book, the witches killed by the Puritans were really magical, and by the Nineteenth Century when this story takes place, witchcraft has been declared illegal. It's a male-dominated society where women are only allowed to be wives or "Sisters", the female equivalent (though subordinate) of the tyrannical "Brothers" who govern New England. Women who are discovered to be witches are either killed, or send away to an asylum from which they seldom return.
When Cate learns that their new governess is a Sister, she's even more frightened. If Sister Elena catches any of them practicing magic, they'll be in real trouble. Worst of all, Cate is nearing the time when she must declare her Intention: to marry or enter the Sisterhood. But, having promised her mother she'd take care of Maura and Tess, how can she choose either of those options?
Close enough to accepted history to be almost disturbing, but different enough that it's not, this fascinating story grabs the reader and pulls her into its World. Cate is a character most females can empathize with , especially if they have sisters (no matter where they fall in the birth order). None of the options open to her are agreeable, but she must choose one. Her decision, and the path she takes to get there, is complex, thrilling and surprising.
Unfortunately, there has been no indication of when the next book in the series might be expected, but it won't be soon enough!
*FLC Full Disclosure: I purchased this book at the inaugural Passion & Prose event in Long Beach.