The Name of the Star by Maureen Johnson

• When Rory Deveaux moves from Louisiana to England, she opts to go to boarding school in London rather than live in the country with her parents.
• At the same time of Rory's arrival, a murderer starts recreating the violent and gory murders of Jack the Ripper -- and right in the neighborhood of her new school.
• After a near-death experience, Rory starts seeing people who her classmates don't see -- and this newfound ability puts her right in the path of a mysterious and psychopathic killer (as well as a team of supernatural police detectives who are trying to track him down).

Grades 7-12
Book 1 of the Shades of London trilogy

I'm on a bit of a mystery/thriller kick right now, and this one was quite fun and enjoyable.  It's made me want to book a flight to London and soak up the ambiance.