Once a Witch by Carolyn MacCullough

I just started this one today. It fits into my current reading theme of YA paranormals.

Here is the Amazon blurb: Tamsin Greene comes from a long line of witches, and she was supposed to be one of the most Talented among them. But Tamsin's magic never showed up. Now seventeen, Tamsin attends boarding school in Manhattan, far from her family. But when a handsome young professor mistakes her for her very Talented sister, Tamsin agrees to find a lost family heirloom for him. The search—and the stranger—will prove to be more sinister than they first appeared, ultimately sending Tamsin on a treasure hunt through time that will unlock the secret of her true identity, unearth the sins of her family, and unleash a power so vengeful that it could destroy them all. This is a spellbinding display of storytelling that will exhilarate, enthrall, and thoroughly enchant.

Here is a really cool YouTube book trailer:

Here is a web site devoted to the book. And here is a link to the author's blog.