The Doors of Eden

Lee and her girlfriend Mal are investigating an alleged monster sighting when Mal suddenly disappears in a blizzard. Mal's mysterious return 4 years later is of interest to MI5 agent Julian Sabreur. He's investigating a crime committed by a group of people who don't quite look human, and Mal is somehow involved.

Then the sci-fi aspect of this novel kicks in as it's revealed there are worlds parallel to our own Earth. Evolution has diverged at a different point in each world and created a different dominant species. As cracks form between worlds and monsters slip through, humanity may lose its position at the top of the food chain.

I would have preferred to see more of Lee and Mal, and less of the MI5 agent Julian. He's less of a suave James Bond type and more of a grumpy everyday man with a struggling marriage. How much you like him probably depends on how well you can relate to him.

The parts of the other parallel worlds that we did get to see were excellent, and I would have loved to read more about that. For me the best part of sci-fi is reading about a completely different setting - whether that's the future or somewhere in space. So the bits set in “present day” Earth weren't as interesting to me.