The Lacuna, By Barbara Kingsolver

At the heart of Barbara Kingsolver's sweeping historical novel lies a reluctant writer, his recalcitrant stenographer and a Nabokovian dilemma: fragments of Harrison William Shepherd's furtively written memoir are stashed in a bank vault by his assistant, Violet Brown, and await posthumous publication despite his wish to have every last sheaf burned in his back garden.

Given the publication of Nabokov's unfinished 'new' novel this month - saved from the incinerator by his wife against his death-bed instructions - Kingsolver ruminates on the same philosophical conundrum on why a writer is compelled to write, if not to be read.

In the case of Shepherd, who is happy penning pulpy Aztec potboilers, his own life story is the one he believes in the least. Despite his diffidence, Violet thinks Shepherd's remarkable life - begun on the shores of post-revolutionary Mexico in 1929 and nearly ended in McCarthyist North Carolina of the 1950s - does not warrant self-censure. Yet her loyal endeavour to save his words from oblivion is her greatest transgression.

As the son of a spirited Mexican flapper and spineless American father, Shepherd lives peripatetically, zigzagging across borders after his mother flees her marriage in hope of a wealthier 'upgrade' in Mexico's Isla Pixol. He vacillates, forever an outsider, from an American military school, back again to Diego Rivera's New Mexico, in whose Communist household he begins his 'below stairs' ascent from cook to secretary, and procedes to become a bestselling American novelist in Asheville, before his patriotism is questioned in front of the 'House Committee on Un-American Activities'.

The dynamics of the most famous of Mexican households are enacted with vigour, from the marriage of the toad- faced muralist, Rivera, to his "Azteca queen" wife, Frida Kahlo, and the Russian exile, Leon Trotsky, endearingly nicknamed "Lev" who seeks temporary refuge in Rivera's home and whose ideals inspire Shepherd to transform himself from the amanuensis of great men to a man of letters himself. "Where does any man go to be free, whether he is rich or poor or even in prison? To Dostoyevsky? To Gogol!" says Trotsky, rousingly.

Kingsolver uses the opening image of a group of monkeys in Isla Pixol, dubbed 'Howlers' by locals, as a metaphor for political hysteria. "It starts with just one of them groaning: a forced, steady rhythm like a saw blade. That arouses others near him, nudging them into bawling along with this monstrous tune." We see such political choruses bellow through the book's history: from the voices of dissent against Trotsky which develop into thundering protests to the trickle of media reports accusing Shepherd of being a Communist, ending in life threatening crescendo.

Yet Kingsolver's marriage of the personal and political form an uncomfortable alliance. Having excelled at interweaving the greater story of the Belgian Congo with the intimate child subjectivities in her best-selling novel, The Poisonwood Bible, Kingsolver ends up treading on the fringes of her characters' inner lives in this latest work. Perhaps the historical arc of the novel - stretching from the Bonus Marchers of 1932 to the aftermath of the Second World War, Mexican Communism and McCarthy's witch-hunts - is simply too wide, and realised at the expense of characterisations. The emotional fall-out from Trotsky's affair with Kahlo is barely addressed. Shepherd's homosexual cravings are only intermittanly alluded to after he is excused from Military Service as a "blue slip". There are times when Kingsolver offers a glimpse of his pent-up passions – his sexual longing for Trotsky's assistant, Van, after he discovers Van is to leave Mexico, is one such moment: "Van evanescent, servant of the advance, praise any word that could hold you. Praise your jacket that hangs on the peg...The Flemish lilting of your words, like the shift and drop of a typewriter carriage: a library with poppy fields inside." There are not enough passages carrying such poetic emotional disclosure. We are returned to the lessons of history, sometimes barely disguised, and the ways in which politics intersects individual destinies.

Shepherd, writer and protagonist, remains frustratingly illusive, described in fragments - diary entries, letters to and from Kahlo, media reports - which are like disembodied limbs pasted together in an attempt to create a full-bodied portrait. Perhaps it is the success of a novel that seeks to prove the impenetrability of its central subject that also serves as its failure.