Case Keenum’s ascension as the Minnesota Vikings’ starting quarterback on their run to the NFC championship game last fall was a feel-good story so surprising it could have been taken straight from the pages of a thrilling sports novel. So it shouldn’t surprise that Keenum’s football journey will be documented in an upcoming book — written by the now Broncos’ starting quarterback. “Playing for More: Trust Beyond What You Can See” is set for a September release and is available now for pre-order.