While the concept is amusing, and this story has its moments, the joke gets a little stale after a while. Brett creates a fun old-fashioned British Aristocrat mystery that is unfortunately too heavy on caricatures- the beautiful, but secretly clever heiress, her handsome and good-natured but ridiculously vacuous brother, the evil foreigners, the dependable but sadly lower class butler, etc. The mystery/adventure plot was slight and barely carried this farce into the three star realm for me. 
 Basically, it was amusing enough for a lark, but not worth continued reading in the series.