By KEN TUCKER

Estrin propels the wriggly, six-legged Samsa through the first half of the 20th century, where he has vigorous verbal encounters with, among many others, Ludwig Wittgenstein, Robert Musil, Charles Ives and Albert Einstein. He even turns up as a surprise witness in the Scopes monkey trial. Samsa becomes a pop-culture sensation -- 1920's flappers bend their limbs to a new dance, ''the Gregor.'' He takes a job at Ives's insurance company, where he devises the theory of risk management, and eventually contributes to the World War II effort, for which he is given an appropriately small, dank office in the basement of the White House by Franklin D. Roosevelt. (Eleanor Roosevelt, presaging the concept of political correctness, refers gently to Gregor as a ''roach person.'')

This literary bugatelle could easily have become excruciatingly cute; I feared the worst early on, when Estrin has Musil -- the author of the exquisitely interminable novel ''The Man Without Qualities,'' here amusingly portrayed as a ponderous bore -- refer to Gregor as ''Herr Larva.'' But as ''Insect Dreams'' proceeds, it takes on its own logic. Having first contradicted Kafka in deciding that the charwoman employed by Gregor's parents did not dispose of their monstrous son, Estrin, like Gregor, is liberated to explore the implications of human intelligence trapped in a cracked carapace (remember the apple the appalled Papa Samsa throws so violently it permanently wounds his son?). Treated first as a freak-show novelty, then as a scuttling savant, Gregor becomes a complex figure in Estrin's imagination. He's a troubled soul, ''the sum of his confusions''; a humble bourgeois whose physical transformation also alters his inner self: he finds himself debating the morality of the atomic bomb with J. Robert Oppenheimer, as well as experiencing a longing for a woman so intense he contemplates amputating two legs to approximate more closely a human's four limbs. This is the ''half life'' of Estrin's subtitle: as a creature incapable of fully inhabiting either the insect world or humanity, he settles for working hard, as industriously as a burrowing bug, to move history in what he thinks is the proper direction.

Estrin, who refers to Gregor as a ''5-foot-6-inch cockroach,'' has either opted not to read or (more likely) chosen to ignore Vladimir Nabokov's Cornell lecture on ''The Metamorphosis,'' in which the novelist-naturalist declared that, given Kafka's description, Samsa could not be a cockroach but rather was a beetle, and only three feet long at that. But Estrin's portrayal of Gregor does echo Nabokov's judgment of Kafka's writing, that ''no poetical metaphors ornament his stark black-and-white story; the limpidity of his style stresses the dark richness of his fantasy.'' Estrin, who is also a cellist, has music in his prose. After describing a Wittgenstein forced to teach grade school for money and taking his bitterness out on his students, Estrin notes of his ever-sensitive man-roach: ''If human character is infinitely plastic, he worried, what is to stop these children from being entirely formed by the resentments of their elders? He carried one such wound in his own back, unhealing, a permanent crater in his soul.''

Like his version of Kafka's creation, Estrin, with his appropriated Gregor, is busy ''building history from venomous scares,'' and furthering that history with a wit deepened by a vivid depiction of a pained creature suffused with generosity, curiosity and heroic persistence.

Ken Tucker is critic at large for Entertainment Weekly.