I was moderately impressed by the
audio original version of this story, but I really liked the book. It is a real shame that Barry Letts has written so few Who novels; his
Doctor Who and the Dæmons is one of the best Third Doctor novelisations. It's an enjoyable romp round the Brigadier's elderly relative's Italian castle, largely but not entirely told from Sarah Jane Smith's pov, with a little bit of coloration from Letts' own theological speculations. Definitely one of the Missing Adventures to look out for (and thanks,
cassiphone, for sending it to me).