Twelve years in the wilderness: In “Steve Jobs in Exile,” Geoffrey Cain delves into the quest undertaken by Apple Computer’s boy wonder as he tries to build his next venture, NeXT Inc. It’s not an untold story, the book’s subtitle notwithstanding, but it certainly hasn’t received the attention it gets here. And while it comes with a happy ending, the route it takes is both tortuous and fascinating. The years in question stretch from 1985, when Jobs was fired from Apple after repeated run-ins with John Sculley—the PepsiCo president he had chosen to head the company—to 1997, when Jobs ended…