Cryptozoic by Brian Aldiss is an unusual time travel story. A new drug called CSD puts your body into a coma-like state while your mind travels into the distant past. Once there, you cannot change anything. You can’t drink the water or collect stones, or hunt dinosoars: all you can do is observe. Time travelers can see and interact with other time travellers, though, who are not always friendly. Out of the reaches of the law, prehistoric eras are lawless and dangerous– not because of wild animals (that can’t see or touch you) but because of other time travellers.

The story follows an artist, Edward Bush, who visits distant times to research and capture in his art. When he returns to the present, three years have passed. His mother is dead, his father is an alcoholic, his employer has disappeared, and the country is under a military dictatorship ruled by a man called General Bolt.

Bush is completely addicted to CSD and time travel. And he is not the only one. CSD addiction has become an epidemic, as more and more people “mind” back into the past, leaving the economy and society of the present in tatters. Bush is enlisted, or more accurately, coerced into the army and is trained to become a time traveling spy. He is given a secret mission and a load of CSD. 

In Cryptozoic, nothing is quite what it seems, and reality keeps shifting beneath your feet. The twists at the end of the book are brilliant and unexpected. This is not a happy-ending hero-saves-the-day book. Instead, the overall tone is one of paranoia, confusion and unease.