Book excerpt: This study follows the lives and ideas of the Yazıcıoğlu brothers Mehmed Yazıcıoğlu and Ahmed Bican, Sufis of the frontier city of Gelibolu and authors of the most popular religious writings in Ottoman Turkish. Carlos Grenier places the Yazıcıoğlus' durable religious vision within their dynamic historical moment on the contested Ottoman borderlands. Examining how these non-elite writers deployed their own intellectual resources, he considers how they approached the religious sciences of the wider Islamic world. And he looks at how they created a religious synthesis appropriate for their own community, the growing Turcophone Muslim population of the Balkans and Anatolia.