My Favorite Book in 2012.
I'd have to say it is the conclusion of Galen Beckett's Wyrdwood series, The Master of Heathcrest Hall. The first in the series was The Magicians and Mrs. Quent, the middle volume was The House on Durrow Street. I highly recommend the whole series - its a mashup with magic, theatre, and Regency romance. Find more at
http://wyrdwood.net/mrsquent/ .