An excellent book, and with just a few adjustments I think Sarah Waters could produce a truly great novel. Waters already does several things well; her writing is measured but of high quality, she does an excellent job of creating a sense of place and the rythms of life in a different time, and her lesbian romances are +++. All she really needs to do is jazz things up a bit. For instance, rather than setting the book in that worst of all islands, Britain, could she instead set it in space? Or maybe a wizarding boarding school/college? Could one of the characters be a dragon, or maybe a star-ship AI? With just a few small changes like this she could earn the coveted "5 star" rating for her next book.
Oh right, the plot. After WWI, downwardly mobile British lesbians find each other, slow romance, and due to economic anxiety they turn to Sweeney-Todding the guests at their rental house, selling off the items and assets of the murdered guests in order to make ends meet while trying to hide the murders from the police, a Mom, and a nosily investigative neighbor. It is a story as old as time.