The customer at the counter of West Side Books in North Denver was trading thoughts with Terry, the ponytailed, bespectacled, thoughtful employee at the register. Which Jack Kerouac book should he start with? “On the Road,” Terry answered, then added, “It’s probably easiest.” Somehow that sounded like the kind of understatedly perfect advice one so often receives at an independent bookstore. Cheryl Strayed — author of “Wild” — headlines Illumination’s Sept.