This was one of the great unknowns of Doctor Who. An original Doctor Who movie for the 1970s, Doctor Who Meets Scratchman (occasionally Doctor Who and the Big Game, which is a less exciting title) was a script written by Tom Baker and Ian Marter to feature themselves and Elisabeth Sladen. It never happened, and the details of it were left obscure until 2007 when Marcus Hearn uncovered the original scripts and wrote an in-depth article on it. Before this, we knew that it involved the Doctor facing a figure that may have been the Devil himself, and that they wanted to get Vincent Price for the role (there was also a plan to get Twiggy on as the companion when it looked increasingly unlikely it would involve Sladen and Marter).
Then came the announcement that Tom Baker himself was to novelise the script. In fact, at first James Goss was down to write it, following his successful novelisations of City of Death, The Pirate Planet and the other great unmade movie project, The Krikkitmen. With all the Douglas Adams scripts covered, Scratchman was the only Tom Baker script left to novelise, unless they try to get a book out of Exploration Earth. It turns out that Goss's name was just a placeholder to keep the surprise of Baker's authorship under wraps, although I suspect he had at least some involvement, since some of the prose does sound like his. On the other hand, Baker is an established writer himself (treat yourself to the wonderfully disturbing children's book The Boy Who Kicked Pigs), and much of it just sounds like pure Tom.
We'll never really know just how much of it was Tom's own work, how much was from Marter's scripting, and how much was assisted with by Goss, but the final result is an absolute joy. There have been a couple of novels told first person by the Doctor, and the Fourth Doctor at that, but they never really feel like they're actually giving us a glimpse of the Doctor's personality. Tom Baker, of course, knows his Doctor inside-out, and it's a pleasure to have him tell the story. The book is full of wry observations, non sequiturs and absurd metaphors, but the silliness doesn't overtake the mounting horror of the book. To begin with, the misfortune is no greater than a trampled picnic (but even the Doctor seems ready to burst into tears at that), building to the extermination of an island population as they are horribly transformed into scarecrows. It sounds ridiculous and probably would have looked so on screen, but in prose it's nightmarish. The scarecrows, weirdly enough, are a vanguard for the Cybermen, who have allied with Scratchman foolishly. It's a sort of dry-run for a Cyber-conversion virus. On the island, though, even these deadly threats pale into comparison with the dreadful local busybody, Mavis Tulloch...
The second half of the book takes place in Scratchman's dimension, going full-on surreal and delving into some truly unnerving imagery. Whether Scratchman is the Devil or not (and that would open up a few continuity questions with the other Devils on Doctor Who) he's a being who revels in fear and power and forces nightmarish visions on his victims.In fact, visions of the past and future are a big part of this story. The Doctor faces visions of his past enemies, and even scarecrow versions of his former selves, but there's also signs of things to come. Sarah sees her own future adventures up to and including her own spin-off series, and there are sneaky cameos by the Tenth and Thirteenth Doctors. It's very much a modern reworking of the old script, using the intervening decades to add all sorts of nods and winks to the story. The entire tale is folded into a framing story where the Doctor has to justify his adventures to (yet another) Time Lord court. So, really, the entire thing is a vision, and who knows just how much is true?
Scratchman is a daft old romp while also being a solid horror story, which is about as perfect an evocation of the prime of Tom Baker's Doctor Who tenure as it's possible to be. It's a tragedy that neither Sladen nor Marter are here to see it finally come to fruition (Marter presumably would have co-written this with Baker had he not died so tragically young). It's even better listened to, with Baker giving his all with an absolutely raucous narration. Easily one of the most entertaining Doctor Who novels in years, and probably far better than a movie ever could have been.
Placement: Sarah and Harry have already encountered the Loch Ness Monster, so it's after Terror of the Zygons. They're taking a holiday when the story starts, so this is presumably a breather after The Android Invasion and before The Brain of Morbius, when Sarah is back to travelling with the Doctor alone.