T he Florida Keys: From Key Largo to Key West , by Joy Williams, published by Random House, is an exceptionally good all-around guide. The author—a novelist—is witty, sharply perceptive, and seems to know every restaurant and motel as well as every roadside or historical curiosity. The Railroad That Died at Sea , by Pat Parks, published by Key West’s Langley Press, gives a fuller story of the train line. For a lavish brochure that gives information and rates for virtually every accommodation in the Keys, dial 1-800-FLA-KEYS. For other general information, call the State Tourism Office, 904-487-1462.