Around the time that David Mitchell was writing his epic, polyphonic, pan-historical novel, Cloud Atlas, a 13-year-old Japanese boy named Naoki Higashida was working on a kind of memoir about his own autism. Naoki’s condition was severe enough that he could only do this by pointing to the relevant characters on a custom-made cardboard alphabet grid. With great effort and patient assistance, he compiled a list of answers to the most frequently asked questions about his behaviour. The resulting book was titled The Reason I Jump, and first published in Japan almost a decade ago. David Mitchell didn’t hear of it until years later, when his own young son was diagnosed with autism. “Before that, I had no reason to know anything about it,” says Mitchell.