The writing of Pen Stewart spans multiple genres, from fantasy, science fiction, dystopia, steam-punk to magical realism. Typical of her stories are the social commitment and accessible, smooth writing style. The stories are not so much genre in itself, the genre is used to focus on the deeper layers of the story and reinforcing them. Deeper layers repeatedly touching topics we have to deal with in everyday life: discrimination, terror, religious violence, euthanasia, animal abuse, women's rights, gender, etc.…

Pen has an aversion to the void, and with each story she is trying to find a balance between the adventurous and the thoughtful, the journey of the characters and the deeper layers of the story that make us think as a human about the world around us, stripped of all frills.

In recent years she has received several nominations and prizes at writing competitions. In 2009 her first manuscript became fourth in an international manuscript competition with Renate Dorrestein as guest of honour. In 2012, Pen was on the long-list for the Luitingh fantasy writing contest. In 2013, she won the Feniks Prize with her story "Nanokanaries en Olifantenhersenen" at the Paul Harland Prize (currently known as the Harland Awards), the longest-running short story contest for the fantastic genre in the Low Countries, and in 2014 she received an honourable mention for the Azra Magazine writing contest of literary publisher Parelz. In 2016, she achieved a top-10 ranking at the Harland Awards, out of a total of 200 entries. More recently, in 2017, Pen was nominated in the Netherlands for the EdgeZero Award.

Her debut was made in 2015 with Uitgeverij Het Punt: an anthology of short stories and one novella, all kinds of high-flyers of past writing contests: "Nanokanaries en Olifantenhersenen". This compendium of stories was followed by "Tijd M. A. N. Chine", a story collection with the same format as the first one. At the end of 2017 her first fantasy novel "Wintercode" was published at the regular quality publishing house for the imagination genre, Quasis Uitgevers.

In the middle of the first lockdown period of 2020, she signed two contracts with another regular quality publishing house: Hamley Books, a trendsetter in the Flemish publishing landscape, for her YA and possibly future thriller and youth books. In 2021 and 2022 two YA books by her hand will be released there. Her fantasy books for adults, such as Wintercode, the sequels, and the prequel series, will remain with Quasis Uitgevers.