He’s one of country music’s most celebrated singers. But Kenny Chesney’s latest work is a book, “Heart Life Music,” in which he describes his life’s journey, from East Tennessee, to No Shoes Nation and beyond. Chesney sits down with Lee Cowan in the Florida Keys, where the country superstar is just another laid-back local, to talk about family, touring, and how he recovered from a 2009 concert which he describes as “hitting a wall.”