This is, so far, the only episode of either series based on a novel. The novel in question was called Human Nature. It was written by Paul Cornell and features the Seventh Doctor and Bernice Summerfield running around in 1914, with the Doctor disguised as a human. This one has the Tenth and Martha Jones, and again features the Doctor as a human. This is one of those really great emotional stories that Doctor Who does from time to time. One thing the new series has consistently done well is to highlight the loneliness of the Doctor. Thats always been present, but it does seem to have become more acute with him being the last of the Time Lords. His relationship with Nurse Redfern really sold this story, as did the horribly creepy performances by the actors playing the Family of Blood. A quiet, wonderful story all around.