There is no doubt that Robert Charles Wilson is a great science fiction writer. His last book, Mysterium, won the Philip K. Dick Award and his last four novels were all New York Times Notable Books. However, with Darwinia, the Toronto author has made a misstep that undermines this latest offering.

The novel opens in 1912 after some inexplicable force has transformed Europe. The new Europe – called Darwinia – is geographically unchanged but devoid of humans or signs of their habitation and filled with plants and animals that appear to have evolved on a different world.

The first half of Darwinia follows the travails of Guilford Law, a member of an early American expedition into the heart of the new Europe. Members of the expedition eventually discover a vast, empty city and learn why Europe has been transformed. It happens that the world Law is exploring is actually a simulated reproduction of Earth running on a vast archival computer far in the future, long after the real Earth has grown old and died. Europe has changed because the simulation has been damaged by the “psions,” bad-guy bits of computer program. The second half of the book deals with Law deciding to aid the good guys and the final fight when he does.

Wilson’s skills as a stylist move the story along and give us honest, human characters. However, writers of fantasy know if you are going to use magic you have to clearly spell out the rules for its use. In Darwinia the technology of the psions and the “good guys” is so advanced that it might as well be magic but it is never clearly explained what the limits of the technology are. Why can’t the good guys just restart the simulation? Why can the super-powerful psions only enter Earth through the empty city? What is the timetable driving the actions of the two sides?

Wilson doesn’t properly explain his universe and one is left feeling like the real conflict is going on at a level well above Law’s – and the reader’s – heads. The end result is a beautifully written but virtually incomprehensible story.