With Hybrids, Robert J. Sawyer draws to a close the Neanderthal Parallax trilogy, a trio of books that will likely be looked upon as a career highlight for the Toronto science fiction writer.

As Hybrids opens, the gateway between parallel Earths, discovered in a quantum accident in the first novel in the trilogy, remains open. On one side is our world, the gateway located deep in a nickel mine outside Sudbury. On the other side of the gateway is an Earth populated by Neanderthals (Barasts), technologically advanced and with fundamentally different perspectives on their relationship to their world. Caught between these worlds are human geneticist Mary Vaughan and Barast physicist Ponter Boddit, hoping to conceive the first hybrid child to join their worlds.

Also significant to the novel, and the future of these two worlds, are Cornelius Ruskin – a geneticist and rapist, castrated at the end of the previous novel to protect society – and Jock Krieger, an American military scientist who sees in the Neanderthal world the promise of salvation for the human race.

It is one of the functions of science fiction to hold up a mirror to reality, to allow us to look at ourselves from a different perspective, and to expose us to different possibilities. Sawyer examines everything from religion to vegetarianism, from gender relations to the nature of privacy, from the notions of morality and justice to the construction of race. These ideas are firmly rooted in skillfully drawn characters (particuarly Mary and Boddit) rich in contradictions and self-doubt, and set in a fictional world where these intellectual ideas have life-altering consequences.

Hybrids is a novel of complex ideas wrapped in a tightly plotted, viscerally satisfying narrative. It’s the sort of book one wants to read at least twice; once for the headlong thrill of the story, and again to fully absorb the implications of Sawyer’s thought-provoking ideas.