I think the first Doctor Who spinoff novel I read was Gary Russell's Invasion of the Cat-People, long long ago. I was so deeply unimpressed that it was years before I read another one. Since then, of course, I've become aware of Russell as the host of numerous DVD commentaries and as a talking head on Doctor Who Confidential, not to mention being reminded of his activities as child actor in the Famous Five and editor of Doctor Who Monthly. It's not always a howling success when someone who writes about the genre turns their hand to fiction, but after my recent bout of Serious Reading this seemed like a relaxing option, snagged from the BBC website in electronic form.
And to my relief the book is OK. It's basically a boiled together combination of Doctor Who and the Silurians plus The Sea Devils, with flash forward to Warriors from the Deep, plus some back-story about the breakup of the Brigadier's first marriage and what Liz Shaw was really up to in Cambridge. The book also includes a very nicely done farewell scene between Liz and the Doctor, which of course was not shown on screen. The book could pass as an above-average novelisation of a seven-part TV story, which I think is what the author was aiming at, so can be rated a success.