Barry Letts' last novel, published in 2005 just after New Who began, but taking the Third Doctor, Sarah Jane Smith and the Brigadier to investigate a strange cult based around a mind-altering drug and rescuing Sarah's gormless assistant Jeremy (from The Paradise of Death and The Ghosts of N-Space). It's not great, to be honest; the story rambles and characters make rather arbitrarily stupid decisions in order to prolong the plot. But we should take it as what it is, a farewell note to the series from one of its veteran producers.
This was nominated for the Hugos as the result of a campaign by the author, which also brought several other controversial nominees to the ballot. I'll have more to say about that when I do my Best Novel category roundup, but for now I'll report that this is not quite as awful a book as Correia's Monster Hunter International. However, it's the last book of a trilogy set in an alternate 1930s where many people have psychic/magical powers and the good ol' US of A gets a gang of misfits together on an airship to smite the Asian foe (the Germans having already been dealt with by a zombie outbreak). I'm not moved to find the first two books.