As the sun sinks in the West behind the kiddy pool, erstwhile dude rancher Vanderbilt chats on entertainingly about the history, present practices and romance of the real thing and concludes with reminiscences about his own golden days on the prod in dude-ranching. Brief corrallings of fact complement the photographs old and new: all about early ranches, Spanish and Mexican land grants, development and types of livestock, the management of modern ranches, the cowboy and his doings, soil conservation, etc. -- and dude ranching. Way back that, Mr. Vanderbilt, hosted his pals Will Rogers, Tom Mix and Gary Cooper on his ""Easy Me"" ranch and witnessed a famous put down of hooting wranglers by a first-rate display of horsemanship. Today's dude ranch cowboy stands over six feet tall and earns about $125 a week plus tips. A pleasant book, too tall in the saddle for the trail, but line for the guest house.