Here are some of his notable works:
* The Moslem World: This is arguably his most famous work. It is a collection of articles, essays, and lectures about Islam and missionary work among Muslims. It was first published in 1914 and has been reprinted many times.
* The Unoccupied Mission Fields of the World: This book, written in collaboration with James S. Dennis, advocated for missionary work in new territories, including the Muslim world.
* The Influence of Animism on Islam: This book explores the impact of animistic beliefs and practices on Islam.
* The Law of Apostasy in Islam: Zwemer was a vocal critic of Islam's strict laws on apostasy (leaving Islam).
* Islam and Christian Theology: This book attempts to bridge the theological differences between Christianity and Islam.
* The Glory of the Cross in the Light of the Crescent: This book focuses on the importance of the Christian message for Muslims.
In addition to these books, Zwemer also wrote numerous articles and essays on various topics related to Islam, missions, and the Middle East. He was a prolific writer who used his knowledge and skills to advocate for Christian missions in the Muslim world.
His work was controversial in its time, as it reflected the strong missionary zeal of the early 20th century. However, it remains valuable for its insights into Islam and the history of Christian missions.