This is a great book -- engaging and unafraid of controversy. North of South is a sharp portrait of Africa, sensitive to issues black, white and brown -- and occasionally quite humorous. It's the best, most insightful thing we've read about Africa. A brilliant and provocative observer, Naipaul meditates on the travelers, government officials, shopkeepers and European exiles he encounters on a six-month-long journey through Kenya, Tanzania and Zambia. Fittingly, the book opens at the outdoor cafe of the New Stanley Hotel in Nairobi.  (EAF28, $16.00)