(Harper; 507 pages; $26.99) Reviewed by Joan Frank San Francisco Chronicle, Copyright 2009 Barbara Kingsolver may now rank -- for artistry, longevity and moral purposiveness -- in the 'above reproach' category of authors, gathering distinction with each new work. Her latest novel (her first in nine years) won't disappoint that expectation. Set in milestone-studded history, 'The Lacuna' hauls heavy weight, yet manages it in the intimate, down-to-earth language of journal entries and letters. Their maker is one Harrison Shepherd: shanghaied as a young boy to 1930s Mexico by his Mexican-born mother (a coquette/survivalist), leaving behind a coldly indifferent American father in Washington, D.C. Belonging nowhere, smart little Harrison learns to amuse himself alone, reading all he can and taking up an early, lifelong habit of journal writing -- and (in some of Kingsolver's loveliest writing) swimming at rocky coves, amid '[f]ishes mad with color, striped and dotted, golden bodies, blue heads. Societies of fish, a public, suspended in its watery world.' There he discovers a lacuna, a gap or small tunnel in the rocks, which seems to promise passage to an alternate world. It's an enchanting image and metaphor (for what is missing or not seen, for artistic and human possibility), echoing through all that follows. Soon the bookish boy (his loneliness compounded by his attraction to men) becomes involved with towering personalities: first as plaster-maker for the volatile muralist Diego Rivera, then as cook to Rivera's wife, the indomitable Frida Kahlo, and finally as secretary to Lev Trotsky, who's fleeing the murderous Stalinist regime. Young Harrison grows close to each, imprinted by their natures. Kingsolver renders these figures on a winningly human scale, if a bit predictably: Rivera's an obsessed sybarite, Kahlo a flamboyant, gritty crusader, Trotsky a gentle, courageous believer. In a plot whose delicious currents and confluences at first feel effortless, Harrison eventually migrates to Asheville, N.C., where he acquires a devoted helpmeet, the good widow Violet Brown, and commences his real work: writing novels. Kingsolver's exploration (through all five senses) of Mexican and American geographies, weather, people, food, cultures, politics, languages and era-bound events -- Hoover through World War II, Truman, Nagasaki -- is masterful, and a reader receives the great gift of entering not one but several worlds. In the bargain, Kingsolver mulls the lonely rhythms of an artist's life, including the mind-bending haplessness of enduring both rave and ruinous reviews. Frida counsels Harrison: 'Listen, don't ever become famous. It's killing. You should see what they wrote in the papers, those reviewers. ... They write what they think you should be painting.' 'The Lacuna' is a supremely ambitious work: a dense picaresque, glitteringly alive (particularly in the Mexico sections). Its lone flaw is the occasional pong of polemic. Though Kingsolver salts her characters and their fortunes with apt complexity, historic injustices are relived in such a way as to herd readers pointedly toward a response of moral outrage. Dialogue, too, at times takes on a textbookish tone: 'You want to hear [the House Un-American Activities Committee's] criteria? Any one of the following is sufficient. ... [Refusal] to condemn the Soviet Union. ... [A]ccolades from the Communist Press. Or ... an anti-American bias, despite professions of love for America.' 'So. If you love America, but you hate the segregation laws ...' 'Yes. That could arguably be an anti-American bias.' As Kingsolver is an acknowledged human rights champion (she has established a writing award under that rubric and herself won the National Humanities Medal), this won't surprise. But wielded too blatantly, it can nearly stomp the life out of a story. The book's latter third, chronicling the deadly momentum of anti-Communist witch hunts, feels so heavy-handed it almost derails a reader's caring. In its last section, however, Kingsolver rescues her epic with an intricate, moving, deeply satisfying close, against the landscape she conveys best. The final pages haunt me still. Above all, in Harrison Shepherd, Kingsolver has given us a marvelous being: wry, damaged, tender, wrenchingly decent. There's a lot of Billy Budd about Harrison. (He'd hate hearing that.) You want to shout at him, make him soup -- knowing how sharply, by novel's end, you will miss him. But wait! 'Mr. Shepherd, where be ye?' Violet Brown asks herself toward the end, in what's by then become an endearing refrain. 'And here is an answer,' she decides: 'in [his] books.' 'I could always find him there.' 