Reading Theroux may make you cancel your plane tickets and settle in at home instead for a great read. The sometime novelist (The Mosquito Coast) is at his most masterful with Dark Star Safari, which charts his recent and rocky trek through Africa. From a trip down the Zambezi River with an eccentric, doped-up boatman to a politically enlightening visit with a white Zimbabwean farmer, Theroux embeds himself in the daily life of the continent as few tourists could, or would dare. As he crosses the border into Malawi, he recalls filling out a visa application form: ''Under 'Occupation' I wrote 'Teacher,' though I wanted to write 'Provocateur.''' Theroux has earned the right to call himself both.