THE WAY OF THE TROUT: An Essay on Anglers, Wild Fish, and Running Water by M. R. Montgomery (Alfred A. Knopf: $22; 288 pp.). One of the attractions of fishing books is that they usually keep the metaphysical baloney--if not the deli variety--to a minimum. No references to "the playing field of the mind," as in too many baseball books; no analogies to battlefields and weekend warriors, as in football books. If you write well about fishing, you write about definite skills--fly-tying and fly-casting, fish-studying and current-watching--and so don't need metaphysics. "The Way of the Trout," by Boston Globe columnist M. R. Montgomery, is an exemplary fishing book, for the author never strays far from trout, flies, and the river; the closest he comes to drawing a life lesson from his 40-odd years on the water is to write, toward the end of the book: "I have, slowly, gotten better about paying attention to my own bank, not worrying so much about what is going on across the river." Words to fish by, indeed--though Izaak Walton, who comes in for some memorable criticism here, probably would disagree.