Based on the wonderful TV serial written by Robin Bland (actually a pseudonym for Terrance Dicks, who disapproved of the changes made by the script editor), Terrance Dicks has produced a book worth your reading.
The TARDIS arrives on the planet Karn at the apparent direction of the Time Lords (or maybe it just isn't going where directed). Karn has a number of spaceships which have crashed on it, with apparently no survivors - any who do are being harvested for spare parts by Condo, the servant of Dr. Mehendri Solon. But what is he using them for?
The heavy gothic overtones of this story are wonderful (although probably better if you watch it on video...) and you can plainly see the influence of the movie 'Frankenstein' in many parts. But beyond that, you will see a great Doctor Who story which is not only wonderfully self-contained but extends the back story of the series.