Dark Lord of Derkholm takes place in a magical world somewhere in the vicinity of our own. A ruthless tour promoter, Roland Chesney, has turned this magical world into a kind of real-life Dungeons & Dragons theme park with all that that denotes: raging battles, enchantresses, pirates, dragons, etc. Every year, a new Dark Lord is chosen to oversee these tours and ensure that all works smoothly according to Chesney's plans including the occasional 'pilgrim' marked down as expendable. Thing is, though, when the world is not being forced to host these 'pilgrim parties', it's a pretty quiet place, teenaged angst seemingly the biggest problem they normally face, and the magical denizens of this land like it like that. So, this year they decide to do something. They pay a visit to the Oracle who tells them to make wizard Derk their next Dark Lord. At first, this seems like the perfect choice since most other wizards consider Derk incompetent. Turns out, though, he isn't; he just prefers his own uses of magic which include creating interesting new animals like carnivorous sheep, talking horses, delinquent geese, and flying pigs. He has also created five griffins who he considers his children along with his two human kids.
This unfortunate lack of incompetence presents a problem for the people planning Chesney's overthrow and so they make new plans. Unfortunately, poor Derk and his kids are never informed of these plans to sabotage the tours and, as a result, all kinds of mayhem ensues.
In this novel author Diana Wynne Jones takes a humourous but gentle and fond poke at the themes of Tolkienesque fantasy, its tropes and themes as well as at RPGs like Dungeons & Dragons. In its parody of many of the common fantasy images and characters, it is frequently laugh-out-loud funny and a great tongue-in-cheek romp through what is a familiar landscape to fans of the genre. It's great fun for an adult audience but, despite some death and destruction, it's not too violent for even a younger YA reader.