Richard Flanagan has won the Baillie Gifford Prize for Non-Fiction, the prestigious U.K. literary award, for Question 7.

Flanagan’s book, published in the U.S. by Knopf in September, is a memoir and history hybrid that considers his own family’s past and the purpose of fiction. In a starred review, a critic for Kirkus called the book “a haunting, jagged, sparkling narrative puzzle in which the pieces deliberately refuse to fit.”

The Australian author becomes the first writer to win both the Baillie Gifford Prize and the Booker Prize; he received the latter for his 2014 novel The Narrow Road to the Deep North.

Isabel Hilton, the chair of judges for the Baillie Gifford Prize, said in a statement, “In a year rich in remarkable books, Richard Flanagan’s Question 7 spoke to the judges for its outstanding literary qualities and its profound humanity. This compelling memoir ranges from intimate human relations to an unflinching examination of the horrors of the 20th century, reflecting on unanswerable questions that we must keep asking.”

The Guardian reports that in a prerecorded acceptance speech, Flanagan said he would not accept the prize money—about $63,000—until Baillie Gifford, the investment management firm that sponsors the award, comes up with a plan to reduce its investments in fossil fuels.

The Baillie Gifford Prize was established in 1998. Previous winners include James Shapiro for A Year in the Life of William Shakespeare: 1599; Wade Davis for Into the Silence: The Great War, Mallory, and the Conquest of Everest; and Patrick Radden Keefe for Empire of Pain: The Secret History of the Sackler Dynasty

Michael Schaub is a contributing writer.