This book brings back two old friends, Prof. George Litefoot (from The Talons of Weng-Chiang) and the Zygons (Terror of the Zygons), in what can best be described as a Victorian Horror Romp. Unfortunately the almost-clinical descriptions of gangrene, amputations, and other hazards of the genre don't really work to inspire the Horror, and the story is more padded out than enhanced by the plot twists.
On the good side this story continues the EDA trend of having aliens you can sympathise with, to at least some extent, although it suffers from having more than one Deus ex Machina hiding in the TARDIS.
Over all a fairly solid, but unexciting member of the series.