Image copyright Getty Images Image caption Jeff and MacKenzie Bezos were married for 25 years

MacKenzie Bezos, 48, made headlines this week when she announced she was joining the Giving Pledge - donating half her wealth to charity.

The US novelist, who has a 4% stake in the online retail giant Amazon, is estimated to be worth at least $35.6bn, making her the third-richest woman in the world.

Unlike her high-profile former husband, Amazon founder Jeff Bezos, Ms Bezos is an extremely private person.

She rarely gives interviews, and has generally sought to stay out of the limelight - her Twitter account only has a single tweet.

So what do we know about her?

Ms Bezos, who was born MacKenzie Tuttle, has said she wanted to be a writer from a young age.

"I wrote my first book when I was six... every day after school I'd write a little bit and by the end of the year I had a 142 page book called 'The Book Worm'," she said in an interview with TV journalist Charlie Rose back in 2013.

This love of writing stayed with her - after going to Hotchkiss School in Connecticut, she studied English and creative writing at Princeton University.

Ms Bezos says she applied to Princeton specifically so she could study under Nobel laureate Toni Morrison, who ended up becoming her thesis adviser and an important advocate for her work.

In addition to calling her "one of the best students I've ever had in my creative-writing classes", Morrison introduced her to her literary agent, Amanda Urban.

'Love at first listen'

However - as many authors have found - writing the first novel was a long, difficult process, with a number of detours.

After graduating with the highest honours in 1992, Ms Bezos went to New York.

She told Charlie Rose she had intended to "wait tables and... use my extra hours to write my book".

However, she struggled - both with progressing with her book, and financially.

To pay the bills, she ended up applying for a job at hedge fund D E Shaw - where she was interviewed by Jeff Bezos.

While he offered her a job, she ended up working in another department - but her office was next to his.

"Through the walls I would hear him laughing that giant laugh... it was totally love at first listen," she said.

Image caption Toni Morrison provided a blurb for Ms Bezos' first novel

She told Vogue Magazine she pursued him by suggesting they have lunch - after three months of dating they were engaged, and got married shortly after that.

A year later, Mr Bezos had the idea for Amazon - what he called "this crazy thing that probably wouldn't work".

By most accounts, Ms Bezos was a key part of the start up - driving Mr Bezos to Seattle while he worked on the business plan, and becoming the company's first accountant.

In the years that followed Amazon took off and the couple also became parents to four children.

Ms Bezos' novel-writing ambitions eventually also came to fruition, and her first book, The Testing of Luther Albright, was published in 2005.

'Literary-credentials'

She says the book took her "eight years of daily work", and a fair amount of tears, to complete.

In words that many writers can undoubtedly relate to, she told the Seattle Post-Intelligencer: "Fear and shame made me want to finish. 'Aspiring novelist' is not a job title that does a lot for your ego."

Her first reading was at the Elliot Bay Book Company - an independent book store with a cafe that Mr Bezos had also used for business meetings in the early days of Amazon.

Ms Bezos said that, as a self-described introvert, she "had that feeling of stage fright before a firing squad" before her first reading.

However, Rick Simonson, a senior buyer at the bookshop, recalls that Ms Bezos "carried it off fine" and came across as "well accomplished".

The reading, like many book launches, was "not hugely attended, but there was enthusiasm and warmth" from the audience, he told the BBC.

Image copyright Elliott Bay Book Company Image caption The Elliott Bay Book Company has hosted authors including Haruki Murakami and Salman Rushdie

In the end, while her debut novel, about an emotionally repressed civil engineer and father, did not make the bestseller lists, it was praised by many critics.

A New York Times reviewer called it "quietly absorbing" although with "heavy-handed symbolism", while the Los Angeles Times called Ms Bezos "a smooth and terrifying writer".

The book was shortlisted for the Washington State Book Award, and also won an award from the Before Columbus Foundation.

She also gained the respect of many in Seattle's literary scene.

"My impression was that she was serious about her work... I admired the fact that she kept at it, given everything else she had going on," Mary Ann Gwinn, who was Seattle Times book editor when Ms Bezos' books were published, told the BBC.

Meanwhile, Paul Constant, co-founder of the Seattle Review of Books, says: "I think the thing that was most remarkable about her first book was how competent it was - she could have been published without the Amazon connection."

Ms Bezos' second book, Traps, was published in 2013 by Knopf, a leading publishing house - although many critics considered The Testing of Luther Albright a stronger novel.

One-star review

Ms Bezos has long maintained a low profile on the Amazon website.

Her author profile mentions she "worked a wide variety of jobs, including dishwasher, waitress, clothing salesperson, deli cashier, restaurant hostess, library monitor, data entry clerk, tutor, nanny, and research assistant to Toni Morrison" - but has nothing about her work at Amazon or her marriage to Mr Bezos.

When her first book was published, she told Seattle Post-Intelligencer: "I did not want any influence over buyers on Amazon. People there should treat my book as if they don't know me."

However, she made headlines in 2013 after she posted a one-star review of The Everything Store - a book about Amazon by journalist Brad Stone.

In a 900-word post titled "I wanted to like this book", she accused the book of multiple inaccuracies and said it was lopsided and misleading.

Mr Stone has said that he interviewed more than 300 employees or former employees of Amazon, while his publisher has called the book "scrupulously sourced and reported".

The Amazon association

Despite her efforts to dissociate her writing from her ex-husband's profile - and her decision to be published by Fourth Estate and Knopf, rather than Amazon - you could argue that much of her work has still been eclipsed by the interest in her marriage to the world's richest man.

Mr Constant describes her as a "competent midlist novelist" but adds "I don't think anyone around town really thinks of her as a novelist", given how famous her former spouse is.

Many have also pointed out the acrimonious relationship between Amazon and many bookstores, due to the online retail giant's role in driving book prices down.

The Elliott Bay Book Company hosted a reading of Ms Bezos' second novel in 2013 - and Mr Simonson recalls some people questioning why an independent book shop would want to host a book associated with Amazon.

However, he says: "I felt you can invite the other side in - and she's a legitimate writer who deserved a fair reading".

Image copyright Getty Images Image caption When announcing their divorce, the couple said: "If we had known we would separate after 25 years, we would do it all again"

In January, Mr and Ms Bezos announced they would divorce, saying: "We feel incredibly lucky to have found each other and deeply grateful for every one of the years we have been married to each other."

In April they agreed a record-breaking divorce settlement of at least $35bn, and a month later, Ms Bezos joined the Giving Pledge, a public promise to give half her fortune to charity.

Her writing background came through in her pledge, as she quoted an excerpt from Annie Dillard's The Writing Life: "Do not hoard what seems good for a later place in the book... the impulse to save something good for a better place later is the signal to spend it now."

Ms Bezos wrote: "I have no doubt that tremendous value comes when people act quickly on the impulse to give... we each come by the gifts we have to offer by an infinite series of influences and lucky breaks we can never fully understand.

"In addition to whatever assets life has nurtured in me, I have a disproportionate amount of money to share."

Several Seattle literary figures have expressed hope that she will decide to spend some of that money locally.

"Everyone in the literary community would be thrilled if her personal passion for literature translated into philanthropic giving priorities," says Tree Swenson of Hugo House, a non-profit community writing centre.

There is also speculation over whether Ms Bezos will continue book-writing - and now fully establish her own identity as an author.

As she wrote in her lone tweet in April: "Excited about my own plans. Grateful for the past as I look forward to what comes next."