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When I was young, I devoured the works of science-fiction master Ray Bradbury. In my 20s, I read the science-fiction greats–Heinlein, Ellison, Clarke–trying, like most twentysomethings, to Figure Things Out.

Recently, reading aloud to my children has helped me re-enter that world–sharing J.K. Rowling, J.R.R. Tolkien and Ursula K. Le Guin reminds me that the Big Questions are still so very out there.

Maybe that’s why I picked up “Snowfall” (Tor, $23.95), by Mitchell Smith, a book that ushered me into a world hundreds of years hence, when “climate change” means something more ominous than debates over global warming have led us to expect.

Textual remnants at the beginning of “Snowfall” provide clues to an unexpected chain of events — comets and cometary fragments striking Jupiter’s surface have altered that planet’s, and thence Earth’s, orbit. Earth has been plunged into deep cold. Much of the United States lies under a permanent, mile-high sheet of ice.

“Snowfall” follows the odyssey of Dr. Catania Olsen, physician to a tribe of men, women and children who call themselves “Trappers” and live above the ice sheet in the mountains of the Continental Divide.

The world has been stripped of its civilized comforts. Mankind has been thrown back onto the basics–hunting, trapping–to survive the cold. The continent is ruled by tribes that either war with one another or uneasily coexist.

Olsen has retained some medical knowledge through “copy books,” medical texts copied and recopied by hand so their knowledge will survive. The great works of literature are treasured as gold.

Smith is a meticulous writer who spins an almost-seamless web when creating the Trappers’ world. He stumbles only when introducing plot elements that are never quite explained.