As a boy, Nathan Penlington had loved Choose Your Own Adventures, the literary phenomenon of the 1980s which thrust the reader into the role of main character and compelled them to make decisions and direct the flow of the story. So, when he discovered a job lot of the first 106 adventures for sale on eBay, there was never any question that he would place a bid. When the books arrived, he lost himself in the old adventures. Yet, as he flicked through the pages, there was another story being written - for, in the margins of each book, were the...