Knopf Canada, 280 pp, $34.95, hardcover.

Immigrants often learn what the rest of us rarely do about the provisional, unstable nature of human identity. A sense of self that might have seemed rounded and settled in the old country suddenly appears as one among countless possibilities in the new, something episodic and adaptable to drastically different surroundings.

No one has described this fact with as much persistence and insight as Trinidad-born author V. S. Naipaul, whose career now spans half a century. His latest novel, Magic Seeds, continues the story of Willie Chandran, the detached, furtively observant hero introduced in 2001's Half a Life. Born in India, educated in London, and having donated the prime of his life to a doomed marriage in Mozambique, Willie is, at the opening of this second "half", now adrift in Berlin. There, his idealistic sister gives him "the daily exercise of thinking himself back into more desperate places of the world" and persuades him to enlist in a threadbare army of guerrillas fighting the remnants of an oppressive feudal system in India.

That the middle-aged Willie joins up shows how desperate he has become to lash himself to something organized and purposeful. But what follows in the seven years that he spends as a courier and unlikely gunman for the movement, with all of its vanity, violence, and hollow compromise, shows how easily the individual personality can be swamped and capsized when opened to collective identities, especially of the utopian strain. This point is buttressed by his odd fate in the book's second movement, which is set in London, another society corroded by class resentments. Here, our chameleon of a hero, rescued by well-connected patrons from an Indian jail, meets an addled English aristocrat who finds him a job with a posh magazine.

On the surface, this leap may seem too large to be credible. But Naipaul's crystalline prose is as focused as ever, leaving all of the minute contrasts between shades of moral grey clearly visible and allowing us to draw our own map of the winding passages connecting the "sealed chambers" of Willie's spirit. The result is a dark fable about the forces now pulling at the seams of the world, as once-stable but deeply cruel social orders fall into ruin, and the millions left adrift undergo the painful, often chaotic process of remaking themselves.