FANS of THE EARLY Island-centred fiction of V S. Naipaul, or of the late Harold Sonny Ladoo`s two brief, bright novels, may be interested in Samuel Selvon`s Those Who Eat the Cascadura (TSAR, 182 pages, $10.95 paper). Their interest, however, may be short-lived; the novel, though enjoyable, ultimately fails to rise above the cliches of the genre. Nevertheless, as a hibernating Canadian, I was happy to wallow in the sweat drenched merry-go-round of rural life in Trinidad. Readers familiar with Caribbean fiction will find many of the usual landmarks: raunchy dialogue chased down with dollops of local colour; drunks lolling in the sun, spouting Victorian-era platitudes; immortelle trees stretching up to the sky; British landowners practising fair play by day and droit de seigneur by night; the village shaman, both worshipped and feared; and, of course, the inevitable hurricane, with some wild sex following in its destructive path. A 20-year resident of Britain with 12 books and 20 radio plays to his credit, Selvon, who now makes Calgary his home, follows a well beaten path: the professional writer providing his audience with what they have come to expect. (Note: This is the third version of this title. Besides a 1971 radio play, there is also a 1972 edition under the imprint of Davis-Poynter.)