Directed by Jennifer Kent, "The Babadook" stars Essie Davis as a troubled widow who discovers that her son is telling the truth about a monster that entered their home through the pages of a children's book. (Causeway Films)

The Babadook” is proof that you shouldn’t judge a book by its cover. Based on this Australian horror film’s somewhat conventionally spooky trailer — or even a simple synopsis of the plot, which involves a bogeyman who seems to have stepped out of a picture book by Maurice Sendak’s evil twin — there isn’t all that much to distinguish it from many other similar frightfests.

And yet, as it turns out, the feature debut of writer-director Jennifer Kent is not just genuinely, deeply scary, but also a beautifully told tale of a mother and son, enriched with layers of contradiction and ambiguity.

In its broadest outlines, however, it casts a familiar shadow.

That’s the one thrown by the title character, Mr. Babadook, a top-hatted, claw-footed, black-cloaked ghoul who is the star of a disturbingly child-inappropriate tale that turns up one night on the bookshelf of a little boy. (It hardly seems an accident that the film’s title is an anagram for “A Bad Book.” There’s subtext of sexual predation to the book, the text of which suggests, “Once you see what’s underneath, you’ll wish you were dead.”)

The boy, Sam, played by remarkable 6-year-old actor Noah Wiseman, lives alone with his mother, Amelia (Essie Davis), who is still grieving the loss of her husband (Ben Winspear), who died in a car accident on the way to the hospital the night Sam was born. Amelia has her hands full with the boy, who is not just morbidly afraid of the dark, but also has been acting out at school.

After mother and son read a few pages of the new book one night — before slamming it shut in dismay when they realize its contents — Sam’s behavior becomes even more nightmarish, literally and figuratively. Soon he is building homemade weapons to defend the household against the Babadook, whose presence Sam says he can feel and who appears to affect the electricity in the house, causing lamps to flicker.

That trope will be familiar to fans of the horror genre, along with the spooked dog, black, bile-like vomit and the mysterious reappearance of the book, even after it has been torn to shreds and burned on a barbecue grill. Yet despite these cliches, “The Babadook” has an uncanny freshness.

That’s because of the story’s complex psychological underpinnings. Sam’s mind, which appears to have conjured the hobgoblin that is tormenting him, is bound to his mother’s fragile mental state in a profoundly symbiotic relationship. Whether the Babadook is his demon or hers, or something else entirely — a metaphor for mental illness or an actual monster — is the film’s central question. Kent’s film dances along that line, masterfully balancing the seductive pull of the monster movie with the need for plausible dramatic footing.

“The Babadook” also features visually gorgeous filmmaking, echoing the book’s monochromatic palette of grays and blacks (courtesy of award-winning illustrator Alex Juhasz), then sharpening them with accents of icy blue and blood red. It looks and feels like an art film as much as a thriller.

That’s a difficult juggling act, but Kent pulls it off with style. With its mixture of frights both literal and literary, “The Babadook” will, I suspect, satisfy horror’s devotees as much as the genre’s doubters.

★ ★ ★ ½

Unrated. At West End Cinema and Alamo Drafthouse Cinema. Contains frightening, sometimes violent imagery, crude language and brief sensuality. 93 minutes.