I finished the book this afternoon. First, sorry, Midnight, for bringing politics onto the board--but I must say that the Salem Witch Trials were all about -- in my humble opinion -- politics, and misguided religous fanatics, as DS showed us with Trask, and as LP makes clear in her book.
As for the "last act surprise"...without offering spoilers, the final chapter's revelations, which have been dissed in some board comments, are totally in line with the exposition that we read earlier in the novel, specifically with regards to a certain female character...this is set up very early on, and should not be a surprise to astute readers of the book.
Just my observations and opinions....
Brian