The one book is probably actually three books that were read more or less at the same time: Do Androids Dream of Electric Sheep by Philip K Dick, Little, Big by

The one book is probably actually three books that were read more or less at the same time: Do Androids Dream of Electric Sheep by Philip K Dick, Little, Big by John Crowley, and Shadow of the Torturer by Gene Wolfe. These books led to a change of reading habits in way that led eventually to working in publishing.