A Most Improper Magick by Stephanie Burgis
Her mother was a scandalous witch, her brother has gambled the whole family into debt, and her Step-Mama is determined to sell her oldest sister into a positively Gothic marriage to pay it off--so what can twelve-year-old Kat Stephenson do but take matters directly into her own hands? If only her older sisters hadn’t thwarted her plan to run away to London dressed as a boy and earn a fortune! When Kat makes a midnight foray into her mother’s cabinet of secrets, though, she finds out something she never expected. Her mother wasn’t just a witch, she was a Guardian, a member of a secret Order with staggering magical powers--and Kat is her heir.
Of course, there’s no chance of Kat choosing to join the Order that forbade her parents’ marriage...but Mama’s magical mirror doesn’t seem to understand that. It keeps following her wherever she goes, even when the family travels to Grantham Abbey to meet the sinister Sir Neville, her oldest sister’s chosen fiancé. And what with Sir Neville showing a dangerous interest in Kat’s untapped powers, her mother’s old tutor insisting that she take up her mother’s position as a Guardian, and her sister Angeline refusing to listen to her about anything, *as usual*...well, it’s a good thing Kat kept her boy’s clothing, because she may well have to use it--especially if the rumors of a highwayman are true. [summary from Goodreads]
It's historical fantasy! It's a Tenners book! Kat sounds like she will be a kickass, rebellious, and cheeky protagonist! There's dress-up! (And by that, I mean a girl dresses up like a boy. I'm a sucker for that.)
*sighs happily* I'm content.
A Most Improper Magick will be published in hardcover by Atheneum on April 20, 2010.