The publication date of the new book The Secret of Secrets by world-famous author Dan Brown, whose books Origin, Inferno, The Lost Symbol, The Da Vinci Code, Angels & Demons, Digital Fortress, and Deception Point have topped international bestseller lists and whose works have been translated into many languages and adapted into films, has been announced. The Secret of Secrets will hit shelves simultaneously in seventeen countries, including Türkiye, on September 9, 2025. The novel will be published in Türkiye by Altın Kitaplar under the title “Kadim Sır.” Dan Brown stated in his statement about the book that The Secret of the Secrets is the most complexly structured, most ambitious, and also most entertaining novel he has ever written.