FOR SOMEONE WITH a vested interest in selling goods for exploring the great outdoors, Yvon Chouinard, the owner and founder of the outdoor-apparel company Patagonia, takes a surprisingly stripped-down approach to one of his favorite pastimes. "Heaven knows we fly fishers are suckers for every new gizmo we think will give us a leg up on catching fish," he writes in "Simple Fly Fishing: Techniques for Tenkara and Rod & Reel," to be published by Patagonia Books on Monday. With what could safely be described as ornery skepticism, Mr. Chouinard, along with his co-authors, Craig Mathews and Mauro Mazzo,...