In 1985, the BBC decided to give Doctor Who a "rest" (although rumours persist that they actually cancelled it and were forced to continue due to public outcry...). Several stories were planned and in the writing stage when this edict came down. Three of these stories were novelised by their scripters.
Still trying to give Peri a holiday, the Doctor directs the TARDIS to Tranquela, a country famous for its peace. Unfortunately, their visit coincides with that of the Dwarf Mordant, a member of a manipulative alien race who delight in causing harm to others. And Mordant wants a Time Lord there for his own reasons...
This story is actually quite silly. It is full of clichéd behaviour and situations, and people seem to respond to things in odd ways that don't serve any kind of character development but do progress the plot, such as it is.
While I don't support the BBC's decision to skip a year of Doctor Who production, I am however happy that this one didn't get made.
Really only suitable to say that you have every Doctor Who book.