In Nineteen Hundred Ninety Two, Columbus : CHRISTOPHER UNBORN <i> by Carlos Fuentes; translated from the Spanish by Alfred MacAdam (Farrar, Straus & Giroux: $19.95; 569 pp.; 0-374-12334-9) </i>

Well, hell, this is a protean book: sexy, tumescent, turbulent, rocky, shocky, spermy, wild, controlled and uncontrolled. What it is is masculine. What it is about is Mexico.

“Christopher Unborn” takes place over a nine-month period culminating on that great day in the near future, Oct. 12, 1992, Columbus Day, El Dia de la Raza, the quincentennial of America’s “discovery.”

The Christopher of the title is no Wrong-Way Christo like his namesake. No, this Chris is set ticking by his parents’ copulation on Acapulco Beach on Jan. 6, 1991, with the precise design to win the prize offered to the first male child born in Mexico on the twelfth night of the tenth month in the year of four twenties and twelve.

The novel begins with the hero’s conception and ends with his birth. Shades of “Tristram Shandy,” you might ask? O you bet: As with one of his earlier novels, “A Change of Skin,” Carlos Fuentes exhorts the reader at points to join in, cheerlead the plot, even take over as author. In “Christopher Unborn” he blatantly pleads for comparison not only to Sterne but to Quevedo: “Shandy” is dandy, but picaro is quicker-o, and Christopher’s life in utero is nothing if not picaresque in the highest (lowest?) Spanish tradition of “Lazarillo de Tormes” and Quevedo’s own “El Buscon.”

But to place “Cristobal Nonato” (the original Spanish title of this novel) solely within an Old World tradition is misleading. Fuentes is and always has been, with the possible exception of his Henry Jamesian novel “Aura,” a writer from the word rendered here in the title as “unborn,” can also mean “not born naturally”--a term that, applied by a writer as brilliant as Fuentes, lends piquancy to the history and evolution of what has become The Americas Writing.

What if Japan, instead of Spain, had “discovered” us? What if China had colonized us? Would life in “Make-sicko” City in 1992 be any different? These are but two of the games of conceptual chance “Christopher Unborn” begs us to play. Of course the game of chance of the book, conception-wise, is “Guess What.” “Will I be born?” our hero asks. “Can I love a woman, write a book, free a people?” And furthermore, “READERS, RESOLVE MY DILEMMA: Is it worth it to be born in Mexico in 1992?”

The Mexico of 1992 that Fuentes manufactures for our hero Chris is one part science fiction, one part “Garden of Earthly Delights” and one part Sun ‘n’ Fun Toltec Tour. The nation has been Balkanized (so has the United States! So has Mother Russia!) to help pay off the Eternal Debt. Diego Rivera’s murals have been sold “to the Chase Manhattan Bank in partial payment for interest due, and then transported, yard by epic yard, to Rockefeller Center, where they’d been expected for more than half a century.”

In effect, la patria-- the feminine word meaning both “Mother Country” and “Fatherland,” although Fuentes’ translator favors Fatherland throughout, in homage to Lopez Verlarde’s “Sweet Fatherland” to which Fuentes freely refers-- la patria, masculine-or-otherwise, into which our Chris might-or-might-not tumble, is a mutilated remnant of its former self: a garbage-sodden suffocating graft-invested heap of kaka, “a nation of sad men and happy children,” where nothing works but everything survives, just barely.

Onto this canvas drops our hero-speck Christopher, conceived (and why not?) by two angels, his father (Angel Palomar y Pagoaga) and his mother (the all-suffering Angeles). Crowding ‘round them is a host of villains, uncles, orphans, flunkies, functionaries, into whose innermost thoughts our omniscient fetal narrator allows us to enter because, dear reader, this info is printed in his genes. No sense asking how this works, we’ve all been through it, we are told: “READER, TRY TO UNDERSTAND WHY I CHRISTOPHER KNOW EVERYTHING AND AM AFRAID OF LOSING IT ALL--For each one of the six billion inhabitants of the planet, there are thirty ghosts who accompany him; thirty progenitors, physically disappeared, but alive and kicking in each one of the 100 billion individual genes that occupy each one of the cells of my imminent little body! . . .”

So His Imminence spins us a cracking yarn of betrayal (and sex), of war and corruption (and sex), myth-making (and sex) and religion through Nine Chapters, plus a Prologue (with sex--what did you expect? The Annunciation?).

It is a yarn jam-packed with Sterne digressions and as over-populated as the Mexico the hero might-or-might-not ultimately be born into, teeming with “parachutists,” Dickensian types who drop in, in Fuentes’ words, for “chatter, yakitiyak, gossip and championship bouts of chin-wagging.” And, again begging for comparison with Dickens, it is, above all, a randy, punning panegyric for the Lost Boy (“Oliver Twist Again Like We Did Last Summer”) whose fate it is to become that sad man in a landscape of happy children.

Fuentes is no sad man, however. The author’s voice does not fulfill the condition he laments: The book explodes with wordplay. With the exception of a delicate and beautifully restrained part called “Your House Is Still So Very Big,” which comes at the beginning of the chapter called “Christopher in Limbo,” there are few pages in this excellent English translation by Alfred MacAdam that aren’t peppered with set-your-tongue-on-fire wordplay. “A straight line is the longest distance between words,” el supremo punster tells us early on, and he holds his stunning pace throughout a half-a-thousand-pages-plus.

Those readers of the opp-sex might feel short-sheeted, as I did, from Page Two onward, owing to the overlooked, ignored, discarded, well-known fact that all human embryonic life begins as female, that sexual differentiation in utero does not occur until the sixth week of gestation--or equivalent to Chapter Six of “Christopher Unborn”--but hang in there, as the author would advise: There’s this little thing the Greeks called anagnorisis coming near the end.

If, as Jimmy Carter once avowed, it’s possible for a man to lust for something in his heart, then Carlos Fuentes has a Cadillac-sized cardiac tumescence for humanity. His is a generous, prodigious talent broadcasting its seed in “Christopher Unborn” just for the thrill of needing to proclaim that no deed’s ever wasted when it’s done for love of man.