Theroux sets his sights on Africa in his latest travelogue. By means of local buses, cattle trucks, hitched rides, trains and canoes, Theroux makes his way across the length of the continent. Revisiting this land of his youth -- he worked there in the 1960s -- on the eve of his 60th birthday, Theroux finds a land more decrepit and downtrodden than when he left. Although it is a sobering look at modern Africa (and he has very little good to say about tourists), Theroux maintains his trademark wit as he recounts meetings with missionaries, aid workers, tourists and natives.  (AFR131, $15.95)