My rating: 4 of 5 stars
In a magical world devastated by packs of other-worldly tourists, a good-hearted wizard Derk is named Dark Lord and must organize the scenic evil - and just maybe free his world from tyranny.
A long time ago, an off-worlder named Mr. Chesney gained an exclusive monopoly on extravagant "Pilgrim Parties" to Derk's world. These tours trample the countryside, deplete resources, demand the energies of all the wizards in the world, and often cause fatalities during epic battles between sham forces of Good and Evil. But Chesney has a powerful demon on his side, so no one dares to break the contract - even though Chesney is the only one benefiting from the arrangement.
Led by a powerful female wizard named Querida, the world's leaders are fighting back: as part of their plan they elect the modest Derk as Dark Lord. He in turn enlists the help of his seven talented children (five of whom are griffins of his own design) and his wife, Mara. Along the way Derk enlists his menagerie of winged pigs and horses, hyper-intelligent geese, invisible cats, and dragons to organize night attacks and epic battles. In spite of these helping wings, paws and claws, everything that can go wrong inevitably will go wrong.
Serious things are at stake in this story, because every year people die on the tours (so the funny premise is actually pretty dark in execution). In a cold-blooded arrangement of Mr. Chesney's, some Pilgrims are marked down for assassination by grasping relatives - they are "expendables" - criminals are forced to work as mercenary armies, and the natives of Derk's world supply bodies for Pilgrims to fight and sometimes kill. It's pure exploitation, infuriating and inescapable.
There are a dizzying number of characters to keep track of, both human and nonhuman. (My personal favorite is Pretty, a derpy winged colt who can talk and causes plenty of mayhem wherever he goes.) Derk is sympathetic, as are his children, and the obstacles of organizing a planet-wide fantasy cliche for the Pilgrims provides plenty of action and interest. It's an entertaining story, a few notches below my absolute favorite Diana Wynne Jones book, Howl's Moving Castle. (Howl is a lighter, funnier send-up of fantasy tropes; less extravagantly plotted but more cohesive as a result.)