In the non-fiction book Touched Out, the title taken from the overstimulation mothers feel from having children touch them all day, writer Amanda Montei writes about her experience of becoming a mother just before the #MeToo movement gained momentum.

As she absorbed the countless stories of women experiencing abuse and violation, she began to recognise how the language of "choice" – often used to undermine mothers – is similarly weaponised in discussions about sex and consent. In Touched Out, Montei reflects on her past experiences with men that were either non-consensual, or consensual but still deeply distressing – experiences she feels we still lack proper language to describe.

She recalls feeling betrayed and used after consenting to encounters with men where she had expected tenderness, romance, or basic respect, only to be left feeling exploited and violated. She explains how, in these moments, “the feeling of getting what I wanted was immediately tainted by what I hadn’t known before consenting.”

This sense of betrayal doesn’t just remain in the realm of the sexual, but resonates throughout the entire book, as Montei reflects on the image and promises about motherhood that she had been presented with before getting pregnant – and the much harsher, harder, lonelier, unsupported and more isolated reality of motherhood that she was left living in.

“The feeling of getting what I wanted was immediately tainted by what I hadn’t known before consenting.”

This idea resonates through Marielle Heller’s Nightbitch, an adaptation of Rachel Yoder’s darkly funny novel about an artist turned stay-at-home mother, who finds that her entire sense of self has disappeared into the repetitive, isolated, overwhelming routine of motherhood.

Only known as Mother, the woman has a husband who travels for work, only returning on weekends (Speak No Evil’s Scoot McNairy, currently cornering the market on useless husbands onscreen and doing it very well), and a toddler who can’t sleep unless he’s lying on top of her.

Through a haze of unwashed clothes, endless baby-and-me events, and her husband’s weaponised incompetence, offers to “babysit” his own son, and his well-rested declarations that he would “love” to be able to stay at home with a child all day, Mother begins to look at her life and wonder how she ended up abandoning her identity as Artist, Adult and Woman. Instead, she had become Maid, Jungle Gym, 1950s Housewife and Mother.

As this questioning and rage begins to grow, so does hair, sharp teeth, and protrusions on her belly that could be… nipples? Mother might be transforming into something more primal, more free, more… canine.Marielle Heller is a genius at exploring provocative, female-focused stories that are small in scale but large in theme, commentary and insight.

Her 2015 film The Diary Of A Teenage Girl was a scaldingly honest portrayal of young female sexuality, while Can You Ever Forgive Me? beautifully explored ego and connection, while centring on a spiky misanthrope. Her interest in Rachel Yoder’s novel feels very on brand, but a book that deals with a magical realism-style blurring of fantasy and reality, a lot of inner monologue, and much more social commentary than plot, was always going to be tricky.

Yoder’s novel, while thin, brims with black humour and visceral, occasionally vicious writing. Mother’s transformation into her alter-ego Nightbitch is thrilling, and Yoder lets us into the character’s internal monologue, which includes her self-loathing judgement of other mothers; her rage against her husband, who wanted an independent, artistic wife without sacrificing anything of his to let her keep her independence or art career; and her searing insights into how the world pretends to revere mothers, while systematically devaluing and disempowering them.

The ideas of Yoder’s novel are all there on the screen, and as Mother, Amy Adams beautifully contrasts the exhausted, performatively smiling, and genuinely doting qualities of the character with a deep well of desire and rage. The discontent of suburban motherhood is perfectly captured with montages showing Mother dishing out the same breakfasts and reading the same bedtime stories, often while wearing the same unwashed slobby sweatpants.

It should not be revelatory or unusual to see a woman with an average body onscreen, but it is, and Mother presents like a real mother, unquestionably beautiful but unglamorous, covering her body in oversized clothes that portray not only insecurity, but the lack of time, energy, support and self-esteem to invest in feeling good about herself.

This focus on the lack of support is vital. It is clear Mother loves being a mother. Her ever-present toddler (played by twins Arleigh Patrick Snowden and Emmett James Snowden) is adorable, and she embraces his vulnerable, playful curiosity with boundless patience and tenderness, even when clearly frustrated or bored out of her mind.

Being a mother is something she experiences with genuine wonderment. But the socialised, gendered, unsupported social construction of motherhood – one filled with images of gentle, feminine, shrinking self-sacrifice instead of fearsome, awesome, primal power – is one that fills her with rage.

This desire to recognise and respect the animalistic fact of childbirth and the ferocious potential of mothers is what the transformation into a dog comes to symbolise. But while in the novel this change is one of darkness, sensuality and of the communal power of a lone dog finding a pack (possibly of other mothers, similarly transformed), with the ever-lingering question of whether this transformation is real or simply Mother losing her mind, onscreen this shift feels more silly, cheeky, removed.

While some of the initial body horror, such as the emergence of tail-like hair from an oozing cyst, feels like Nightbitch might be veering into a more four-legged version of The Substance, the dog imagery is split between Homeward Bound-style visuals, or Mother shoving steak into her mouth in a way that feels more awkward than feral, more socially impolite than raw, ferocious hunger.

Frequent imagined asides, like Mother imagining herself slapping her husband before smiling beatifically at him, also feel a little sitcom-y. Also, the inner monologuing that worked so effectively in the book feels very theatrical and more didactic onscreen. This overall lean towards light silliness, rather than dark subversion, defangs the impact of the visual storytelling, the emotion of the film, and even Mother herself.

An infamously vicious moment in the book has been toned down considerably and happens off-camera, and the ending is infuriating in its Hollywood Happy Ever After-ness. These edits make Mother feel more controllable and contained, instead of letting her run wild, untamed, free.

The ideas of the film are fascinating and important, and Amy Adams is compelling as ever, but Nightbitch needed a bit more bite.

• In cinemas now. Watch the trailer below: