To mark Russell Hoban's 80th birthday David Mitchell pays tribute to Riddley Walker, and recalls how this uncompromising novel took over his imagination during a solitary period in Japan.

Russell Hoban, an illustrator and would-be artist, was decorated for bravery against the Nazis. After returning to New York he found success with stories for children. He then moved to England and achieved cult status with his novel Riddley Walker. Now 77, he aims to write a book each year