For a novelist who has been a Pulitzer Prize finalist, Lydia Millet is not as well known as she deserves to be. It’s not for lack of productivity: In the past two decades, Millet has published 10 works of literary fiction and three books for young adults. The obstacle to broader popularity is most likely her category-defying voice, a slippery blend of lyricism and absurdist humor. She asks profound philosophical questions, yet has a direct, confiding style that doesn’t broadcast high seriousness; she’s not above titling a novel “George Bush, Dark Prince of Love” (2000).

Her ambitious new novel, “Sweet Lamb of Heaven,” is part fast-paced thriller, part quiet meditation on the nature of God. If those two genres don’t quite seem to mesh — well, setting up house in such disjunctions is what Millet does best.

"Sweet Lamb of Heaven" by Lydia Millet. (Norton)

When Anna, a professor married to Ned, a ruthless businessman, gives birth, she begins to hear voices: a constant banter that doesn’t seem to issue from her daughter’s mouth, yet stops when the baby sleeps. Anna sees an ENT and a neurologist. No answers there. She isn’t insane and doesn’t consider herself a likely candidate for communication with the Almighty. “My brain’s a little above average, according to standard aptitude tests, but not far above,” this acerbic narrator reports. “Whatever intelligence I have isn’t rated for the ornate subtlety of the divine.” However, she’s handy with a search engine and learns that her voice delivers snippets from sources as diverse as the Bible, Emily Dickinson, Woody Guthrie, Greek mythology, Marine Corps marching songs and Sanskrit meditation chants.

As soon as her daughter says her first word, the voice abruptly stops.

But Anna develops a more urgent problem. She has fled her loveless marriage and is hiding with her now 6-year-old daughter at a seedy Maine hotel. Ned tracks her down, demanding that they return to Alaska to play-act adorable nuclear family as he launches his political career. Ned is either a normal old sociopath with excellent private detectives or a demon, because he seems to be able to control Anna’s dreams. It becomes increasingly clear that this Bible-toting, clean-living conservative candidate is trying to kill her.

Moreover, Anna discovers that the guests at the motel have converged on this unlikely spot in winter for a reason: They all hear voices. They are, in fact, an ad hoc support group for those tuned to the mystery voiceover channel. The other guests learned about the group online, but Anna did not. So how did she wind up there? The hotel’s proprietor suggests that maybe “migration was encoded in her genes,” as it is for salmon, or the dung beetles that use the Milky Way for orientation.

As well as being a novelist, Millet holds a degree in environmental policy and works for the Center for Biological Diversity, an organization focused on protecting endangered species. She shares with Barbara Kingsolver a passionate worry about wildlife’s future: Her 2012 novel “Magnificence” features a bizarre museum of taxidermied extinct animals, and the mermaids in her “Mermaids in Paradise” (2014) are the last of their kind.

In “Sweet Lamb of Heaven,” we learn that one motel guest began to hear the voices when caring for the abused captive orca whales at SeaWorld. Another guest, a botanist, attributes the voices to a certain genus of aspen tree, while another “heard the voice of God from a Pomeranian! Or maybe a shih tzu. She showed us a picture on her phone. She used to carry him around in a Fendi handbag.”

Lydia Millet (Jade Beall)

One support group member insists that human speech is just one aspect of the “deep language” undergirding all of life: “It is language. The same kind that makes your body work without you telling it to. You know how the brain runs your kidneys, say, or tells an embryo how to grow in a pregnant woman? What’s the difference between that kind of implicit, like, limbic OS for our biology — and for the biology of all animals — and just a miracle?”

Of course, the young doctor proposing that mystical explanation is bipolar and suicidal; another guest enjoys a tad too much cocaine. But Anna grows to believe that God and evolution are one and the same, and that those who hear the voice are simply more empathetic and sensitive to “the world that had evolved over millions of years, the mass of living things through which all forms of intelligence cycle . . . the broad, branching tree of evolution that was history and biology and all kinds of astonishing bodies full of ancient knowledge.”

“Sweet Lamb of Heaven” is, in short, a book that Richard Dawkins would enjoy immensely. Millet deserves to be celebrated for staking out territory in which the novel can ruminate about current scientific developments. But that makes her work sound dry or polemical, which it is decidedly not. It’s exuberant and playful. That Millet can smuggle her original insights into a structure featuring a rollicking kidnapping plot and deliciously well-drawn characters makes her achievement even more remarkable.

Lisa Zeidner’s most recent novel is “Love Bomb.” She teaches in the MFA program in creative writing at Rutgers University at Camden.

Read more reviews of Lydia Millet’s novels:

‘Magnificence’

‘How the Dead Dream’

‘Oh Pure and Radiant Heart’

Sweet Lamb of Heaven

By Lydia Millet

Norton. 250 pp. $25.95