Circle of Days is a 704-page historical fiction novel by internationally bestselling author Ken Follett, published by Grand Central Publishing (Hachette) on September 23, 2025. An instant New York Times bestseller, this sweeping epic explores one of history's greatest mysteries: the building of Stonehenge.

Set on the Great Plain of ancient Britain, the story follows three unforgettable characters. Seft is a talented flint miner who walks the Plain in the high summer heat to trade his stone at the Midsummer Fair and to find Neen, the girl he loves. Joia is Neen's sister, a visionary priestess with an unmatched ability to lead who dreams of raising a miraculous stone circle from the largest stones in the world. As drought ravages the earth and mistrust grows between the herders, farmers, and woodlanders of the Plain, an act of savage violence erupts into open warfare—threatening the monumental dream that has united them.

Truly ambitious in scope, Circle of Days showcases the master storytelling that has made Ken Follett one of the world's most beloved authors, with more than 198 million copies of his 38 books sold in over 80 countries. Praise for the novel includes starred reviews from Kirkus Reviews and enthusiastic endorsements from Lee Child, Publishers Weekly, and Booklist. Available in hardcover ($40.00), ebook, audiobook, and trade paperback formats. ISBN: 978-1-5387-7277-5.