Slaves, Tolkien, Tuchman, art; Practicing History: Selected Essays, by Barbara W. Tuchman. New York: Ballantine Books. 306 pp. $7.95.

This book isn't just about writing history. What Tuchman has to say applies to all forms of communication and to both giver and receiver. The author shares her trade secrets in a most entertaining way. She shows how anecdotes rescue historical figures from the misty past and present them as real people. An example, the birthday present Kaiser Wilhelm II gave his wife. Every year without fail he gave her 12 hats - hats he had chosen himself - and which she was obliged to wear. That, says Mrs. Tuchman, reveals something about the Kaiser and the Germany of his day.