Dr. Paul Sears' Lands Beyond the Forest (1968, p. 1331) was a more strenuously cerebral study of the ecology of the open plains for the serious student. Mr. Costello's book is an informal field companion to rambling westward. Although paying his respects to the recent efforts of the climatologists, the author, a native of the Nebraska plains, enjoys the gratifications of his own weather-eyeing: "". . . out on the prairie, the wind and the sky tell more of the beauty, the fury, and the silence than all the thermometers, barometers and weather gauges put together."" Beginning with an overview of the ""Grassland Sea"" that once extended, unviolated by man, from the mid-west to the Rockies, from Canada to the Gulf of Mexico, Mr. Costello tells about the prairie year and its ecology--plants, animals, waters, natural disasters and renewals. Although the conservation admonition here is merely the lightest wrist-slap, nonetheless Mr. Costello does manage to convey his pleasure and intimate knowledge of the still unspoiled areas. With a helpful appendix of information for wildlife-bound visitors, this would be a rewarding knapsack item, unless the weight (62 photographs are promised) would be prohibitive.