Neal Stephenson’s new novel, as his veteran fans will soon discern, is a sequel to his earlier book, “Reamde,” though it’s not touted as such in the marketing material. The reason for this omission might be that, despite featuring the same cast, “Fall” is as different from “Reamde” in tone and purpose as possible. Leave it to this master trickster to have us board a cruise ship we expect to voyage to Club Med, but which instead delivers us to the Twilight Zone.

Cover courtesy of Neal Stephenson.

“Reamde” was an explosive, edge-of-your-seat roller-coaster thriller involving a rich, eccentric, brilliant family – primarily Richard “Dodge” Forthrast and his niece Zula. Set in the present, it featured gangsters and cyberpunks, chases and loot, lots of guns, and some modest excursions into a video-game environment. It had deep things to say about families, love, work, competence and friendship. But those observations were embedded in a sleek adventure – not mindless or superficial by any means, but more surface than depth, frothy and giddy.

By contrast, “Fall” starts in the near future and spans a century. Although its plot points are many and captivating, it is more metaphysical. Two interlocking worlds rather than one share the screen. Its pace is deliberate and leisurely. It also exudes an autumnal melancholy and reveals the deaths of many folks we have come to love – but death with a difference, for the main thrust of the tale concerns immortality made possible through technology.

We begin the story riding the shoulders of middle-aged Dodge, now incalculably wealthy but still vitally engaged with his business and the world. Zula, meanwhile, has a very young daughter, Sophia, whom Dodge dotes on. Dodge is on his way to have a small medical procedure done, and he muses on the strange and wonderful nature of reality – musings resonant with what’s to come. Not to spoil much beyond page 35 of a nearly 900-page novel, I will reveal that Dodge dies on the operating table.

Enter Dodge’s best friend and former employee, Corvallis Kawasaki, who’s named in the will as Dodge’s executor. Corvallis, Zula and other family members, along with some helpers, must carry out Dodge’s posthumous wishes: to have his brain preserved for future resurrection. They do so, though the promised resurrection isn’t possible until Sophia is an adult, and even then, it’s not bodily but as an uploaded avatar in a virtual world.

The antagonist in this scenario is Elmo Shepherd, yet another mega-rich titan who has plans for the digital afterlife that conflict with those of the Forthrast clan.

The slow evolution of Dodge’s afterlife now shifts between “meatspace” and virtual reality. In the carnal sphere, we watch as Corvallis, Zula, Sophia and others leapfrog new technologies – hundreds, then millions of other souls follow Dodge into the afterlife – battle rivals and nurse human frailties, while in the artificial realm, we observe a deracinated, desperate and delusional Dodge become Egdod, the somewhat mad and megalomaniacal deity of the afterlife. As various characters die, they transition to the afterlife under fresh guises. But the unique kicker of this setup is a built-in and inescapable communication barrier.

Using software known as the Landform Visualization Utility, the living humans can observe the silent avatars to an imperfect degree, tracking their behaviors. But it’s one-way communication. Wiped clean, the digitally dead have no knowledge or awareness of where they came from, no renewed contact with those they left behind. Consequently, they must develop a new civilization out of their cybernetic tabula rasa. This frustrating, almost allegorical inequality contours the whole tale.

The passages set in the real world display all of Stephenson’s usual witty brilliance when it comes to technology and culture. Of Zula’s robotic home aide, he writes, “millions must have been spent on the bra-strap-hooking algorithm.” One extended mini-masterpiece involves the biggest Internet hoax ever perpetrated: an event that nets Corvallis his wife and which succeeds in crashing the World Wide Web – or the “Miasma,” as its detractors, grateful for its death, call it. The substitute system that Stephenson blueprints is ingenious, complex and believable. American political fragmentation also gets a rigorous speculative workout. “Ameristan,” anyone?

As for the Miltonic saga of Dodge’s godhood, which gradually comes to dominate the narrative, Stephenson more or less gives us a cyber-“Silmarillion.” Using an unsentimental, natural-sounding bardic voice and the apparatus of Tolkienesque (or E.R. Eddisonian) fantasy, he produces a whole myth cycle that recalls the blended techno-religious fantasy of Roger Zelazny’s “Lord of Light” and the Dungeons & Dragons cyberspace stylings of Vernor Vinge’s “True Names.”

The book’s ending leaves mortals trembling on the precipice of post-human greatness. But Stephenson foresees no arid desert of sterile intellect, only an extension of the human heart, in a touching final image. In cyberspace, Dodge gets to conclude the task that death cut short. A restored-to-childhood Sophia sits on Dodge’s lap, receiving the storytelling session long delayed. The reunion between uncle and child is only a few billion clock cycles away.

Paul Di Filippo’s most recent novel is “The Deadly Kiss-Off.”