The book “What is Islam?” was published in 1979 as part of Dr. Mustafa Mahmoud’s intellectual project, aimed at exploring the relationship between religion, reason, and humanity. In this book, the author discusses the state of contemporary Muslims and their weakening connection to their beliefs. He also explores how worship has become a habit performed without any true spirit, and how the Quran has become a book that is recited without any real guidance for life. The author seeks to understand the true essence of Islam, as described in the Holy Quran. He calls for us to regain this essence, free from the impurities and traditions that have been attached to it over time. He tries to speak to reason with arguments, and to the spirit with the light of faith, in order to reveal Islam as God desires it to be: a religion that values both reason and the heart.