This important work is an historical study of the Islamic writings in Spanish and Aljamiado (Spanish in Arabic script) of the Muslim minorities in medieval Christian Spain, the Mudejars and Moriscos.On the basis of both Christian sources, such as archival documents and the writings of John of Segovia, and Islamic sources in Spanish and Arabic, this book focuses on the life and writings of Yca Gidelli (ca 1450), religious authority of the Mudejar community of Segovia (Castile). Of crucial importance for the history of Islamic Spanish literature, Yca's best-known work is a Spanish translation of the Qur'an made at the request of bishop John of Segovia (d. 1458).This study follows the early history of Islamic writings in the vernacular (13th-14th centuries), continues with a description of Yca's writings and biography, and finally deals with his influence on Moriscos in the 16th and 17th centuries.