THIS SUMMER, an unusual exhibition appeared at Cadillac House—General Motors’ presentation space for “vehicles and brand partnerships”—at the far west end of SoHo in Manhattan. Its subject, Visionaire, is a fashion and art magazine quite unlike any other, and several “issues” were set on pedestals in a dark gallery in the back of Cadillac’s glassy lobby, appearing more like sculptures than pieces of a print publication. Each iteration of Visionaire presents a new challenge to its editors and its readers, in both form and content. Take, for example, the 42nd issue, “Scent,” a pleather, purse-size satchel containing 25 original scents designed by artists, designers, musicians, and models like David Bowie, Kate Moss, Stephen King, Zaha Hadid, and Karl Lagerfeld, whose perfume captures the smell of his favorite Parisian bakery. Or…