Geisler's "Answering Islam: The Crescent in Light of the Cross," provide a detailed comparison of Islam and Christianity by exploring Islamic beliefs about Allah, Muhammad, the Qur’an, and salvation. The book critically assesses Islamic teachings, addresses topics like Qur’anic abrogation and Islamic history, and discusses different sects such as Sunni, Shi’ite, and Sufi, along with the Nation of Islam. The material offers a thorough overview of Islamic faith and practices while presenting arguments from a Christian apologetic standpoint.