In suburban Philadelphia, a young woman leaves a late-night party to babysit a toddler whose parents are dealing with an emergency.

She takes the little girl to an upmarket grocery store, only to get security called on her because she is black, the child is white and they think she is a kidnapper.

So begins American author Kiley Reid's debut novel Such A Fun Age, an instant New York Times bestseller that had its screen rights scooped up by Emmy-winning producer and screenwriter Lena Waithe even before publication and was chosen by actress Reese Witherspoon for her book club.

"I love a high-stakes opening scene," says Reid, 32, over Skype from Philadelphia, where she lives.

"I wanted to experiment with racial bias that is not violent, but still traumatic. At the time when I began writing, the Black Lives Matter movement was under way.

"I was curious what those instances would look like on the page when they're a bit more domestic and close to the ground, but still scary."

Though the novel opens with this racially charged melodrama, Reid then pulls it into the background, where it remains for most of the narrative like a smoking gun.

Instead, the narrative focuses on her protagonist Emira, a 25-year-old part-time babysitter and typist who is struggling with her direction in life.

"For Emira, her blackness is not the only part of her," says Reid.

"She has a lot of different facets to her - her intelligence, her life and her family. There's her growing up, there is her pending problem of being kicked off her parents' health insurance - and all of those things feed into her reaction when the incident happens. She almost blames herself. She tells herself, 'This wouldn't happen if you had a real job.'"

The grocery store incident causes Emira's employer Alix, an affluent blogger with an abundance of "white guilt", to become invested in - even borderline obsessed with - the personal life of the young woman whom she pays to care for her child in her stead.

Emira also starts a relationship with Kelley, an older white man who filmed the incident and wants to post the video online to shame the store. Both he and Alix insist they are acting with Emira's best interests at heart.

Reid was a babysitter and nanny for six years, though she says the novel is not autobiographical - she comes from an upper-middle-class background, unlike her less-privileged protagonist.

"Like Emira, I had a financially precarious time in my 20s," she says. "I went many years without healthcare and was nervous about getting into an accident or having to go to the doctor and not being able to pay for it.

"For a long while, nannying and babysitting were my main sources of income. But the biggest difference is that I always had an end goal - I knew I wanted to write - and Emira doesn't have that passion."

Reid, who is married without children, says she loved babysitting. Still, she hopes her novel can get readers to rethink emotional labour, as well as the ways it intersects with racial and class privilege.

"A big goal of mine was to show a lot of characters and how they're concerned with how their individual actions are perpetuating or not perpetuating racism - did I say the right thing? Did I say the wrong thing?

"The truth is, even if Alix was a perfect mother to babysit for, Emira's standing as a low-status domestic worker wouldn't change.

"Healthcare laws wouldn't change. The fact that white families without college degrees still make more than black families with college degrees, that wouldn't change either.

"I think it's important to realise that power is not being redistributed with this novel. All I can do is write what I hope is a compelling book."

• Such A Fun Age ($22.95) is available here.

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