Alharthi shared the nearly 57,000 euros prize with her translator, American academic Marilyn Booth.
Celestial Bodies is the first book by a female Omani novelist to be translated into English.
It tells the tale of three sistesr: Mayya, Asma and Khawla.
The book is set in the Omani village of al-Awfi, and each sister’s tale centres on a personal disappointment.
Mayya marries into a rich family after a heartbreak. Asma marries out of duty. And Khwala waits for a man who has emigrated to Canada.
Celestial Bodies was chosen from a nearly entirely female and independently published shortlist, including France’s Annie Ernaux, former winner Olga Tokarczuk and Columbia’s Juan Gabriel Vasquez.
Speaking in an interview with the Man Booker organisation after being shortlisted, Alharthi described her book as a glimpse into the “colourful life of an Arab Omani family, particularly three sisters growing up at a pivotal time in Omani history”.
She adds that she hopes readers from around the world will discover that “Oman has an active and talented writing community who live and work for their art.”
In the same interview, translator Booth said she took much pleasure in translating Alharthi’s book because she weaves “stressful and beautiful relationships to life within the complex political and social history of Oman”.
She adds that what makes this book special is the “the use of language, or languages: the distinct idioms or sociolects of differently placed characters, the vivid use of local expressions and usages, in particular the conversations amongst women”.
In an interview with the BBC, Alharthi recounts how her first year in Edinburgh for her PhD, proved to be the impetus to write this book.
“I had the plan for a very long time to write a book about a life in Oman and I couldn’t write about it when I was actually in Oman. But I went to Edinburgh, the first year was difficult for me….so I felt the need to go back to home and feel something from home. So actually writing saved me”.