But here it is, Mason & Dixon, a rollicking, ambitious, dense and difficult novel that in its scope and brilliant reimagining of 18th-century literary style is a worthy successor to Gravity's Rainbow. As in his earlier works, Pynchon combines wicked puns, bawdy songs, encyclopedic knowledge and a gifted eye for finding the profound in the absurd, to track down, but never quite bag, the malevolent forces controlling everyday existence. In Mason & Dixon he explores the underside of the American colonial enterprise, and European imperialism in general, to unravel the historical roots of the racial and social dislocations that haunt his other works and contemporary America.

The novel focuses on Charles Mason and Jeremiah Dixon -- an oddly matched pair of British scientists who joined their lots at Capetown, South Africa in 1761 to measure the transit of Venus across the sun. We then follow the astronomer (Mason) and the surveyor (Dixon) to the New World where they establish the boundary line that bears their names.

Concentrating on actual historical figures somewhat constrains Pynchon's plot-making, but Mason & Dixon is dependent on neither plot nor character in the conventional senses of those terms. Nor are the characters typically Pynchonesque. While earlier protagonists like Oedipa Maas and Tyrone Slothrop engaged in quests after truth, Mason and Dixon serve as foils to the forces who commission their work for ends neither can fully recognize. For Pynchon's real concern is the "world-making" activity represented by the Line. Establishing the Line presents a metaphoric locus for exploring the colonial enterprise as it refashions the new Eden of America into legal and land development parcels, imposing the worst forces of the past on virgin land that had seemed to promise a fresh start.

As they trek through the American wilderness -- encountering caffine abuse, an exiled French chef and revolutionary cells of anti-taxation Americans -- the pair gradually realize the ramifications of their Line separating North from South, although they can only imagine what it will mean in terms of slavery, how it will belie the rhetoric of "equality" upon which the nation would be founded. Dixon wonders: "No matter where in it [the world] we go, shall we find all the World Tyrants and Slaves? America was the one place we should not have found them."

But they do, and in a small personal effort at emancipation, Dixon chooses to intervene and stop a slave dealer from abusing his "property." Of course the effort is isolated, minimal and futile in the long run. But in the ethics of Pynchon's fiction it is the small act of kindness that reveals the true human spirit. History for Pynchon is always a site for fictional invention that looks behind accepted appearances. It is a vehicle for debunking, rather than propagating myths.

In many ways Mason and Dixon are compelling for the same reasons as Maas and Slothrop. Their ordinariness, their perspectives as outside witnesses, they serve as a moral compass. And yet, like their literary predecessors, their humanity is not quite enough to the overwhelming force of the system. Late in the book, Capt. Zhang, a Chinese member of the survey company, observes, "To rule forever it is necessary only to create, among the people one would rule . . .Bad History. Nothing will produce Bad History more directly nor brutally, than drawing a Line, in particular a Right Line, the very Shape of Contempt, through the midst of a People,-- to create thus a Distinction betwixt 'em,-- 'tis the first stroke.-- All else will follow as if predestin'd, unto War and Devastation."

As Mason and Dixon reach its terminus at the "Great Warrior Path," a native American "line" whose spiritual force they choose not to violate by crossing, they come to realize their Line's potential as a "conduit for Evil." Mason or Dixon asks Capt. Zhang, "Right Lines, by minimizing Distance, are highly valu'd by some.-- Commanding Officers, Merchants, Express-Riders?" Zhang replies, "Without Question. Officers kill men in large numbers. Merchants concentrate wealth by beggaring uncounted others. Express-riders distort and injure the very stuff of Time."

Ultimately it will be how their Line is abused that will define Mason and Dixon, making their innocent attempt to complete their contract one more fall from Grace in the Eden of the New World. And yet, in the best Pynchonesque spirit, while Mason, Dixon and the readers are are given clues that strange and powerful forces are at work, we never quite figure out who is behind them.

But the book's deeply serious, almost melancholy tone is leavened with Pynchon's Beat-infused wit. There is an improbable cast of characters with impossible names including Fenders Bodine, an ancestor of Pynchon mainstay Pig Bodine, Professor Voam and his electric eel, and the Ghastly Fop. There's also the Learned English Dog, a mechanical duck and talking clocks. Cameo appearances by some American Founding Fathers -- Mason and Dixon smoke hemp with George Washington and a young Thomas Jefferson cadges the line "the Pursuit of Happiness" from a Dixon barroom toast -- display Pynchon's demythologizing irreverence.

Nevertheless, the satire in Mason & Dixon is more studied and the jokes more mature. The narrative language is often some of his finest, with passages that will make readers both laugh and weep. With Mason & Dixon Pynchon charts the historical ground of American reality while displaying the height of his powers, reasserting his place as one of the preeminent post-war American novelists.

Bernard Duyfhuizen, chair of the English Department at the University of Wisconsin-Eau Claire, is an editor of the scholarly journal Pynchon Notes.