The Revival of the Religious Sciences

Iḥyā′ ‘Ulūm al-Dīn (; ) is an 11th-century book written by Abū Ḥāmid Muḥammad ibn Muḥammad al-Ghazali. The book was composed in Arabic and was based on personal religious experience. It is regarded as one of his chief works and a classic introduction to the pious muslim's way to God. Originally spanning over 40 volumes, it deals with the principles and practices of Islam and demonstrates how these can be made the basis of a reflective religious life, thereby attaining the higher stages of Sufism. 
Some consider Kimiyā-ye Sa'ādat as a rewrite of this work, which is a common misconception. Kimyā-ye Sa'ādat is shorter than this, however Ghazali said that he wrote the former to reflect the nature of the latter and a few of his other theological writings.
Background.
Ghazali was the student of Al-Juwayni, under whom he studied religious sciences, including Islamic law and jurisprudence. Nizam al-Mulk, the Seljuk vizier, recognized the great potential in Ghazali as a scholar and appointed him as the head of Nizamiyya madarasa in Baghdad. Ghazali, at the peak of his fame and scholarship went into a spiritual and intellectual crisis. He left his post at the institution on request of pilgrimage. He went into a long journey, travelling to Damascus, Jerusalem and finally to Mecca to perform the pilgrimage. Ghazali throughout the journey, was going through an inner spiritual struggle, and he became attracted towards the pathway of Sufis. This journey influenced Ghazali to write first on his autobiography "Deliverance from Error" and then his famous book "The Revival of the Religious Sciences", explaining in detail about mysticism, theology, Islamic rituals and practices.
Structure.
The book is divided into four parts, each containing ten books. It explains the doctrines and practices of Islam and showed how these can be made the basis of a profound devotional life, leading to the higher stages of Sufism or mysticism.
This part contains the following books:
This part contains the following books:
This part contains the following books:
Influence.
Seyyed Hossein Nasr states that it is 'perhaps the most influential work on ethics in Islamic history'. It became the most frequently read Islamic book after the Quran and the hadith. Its great accomplishment was to bring orthodox Sunni theology and Sufi mysticism together in a useful, comprehensible manner to guide every aspect of Muslim life and death. The book was well received by Islamic scholars such as Nawawi who stated that: "Were the books of Islam all to be lost, excepting only the "Ihya", it would suffice to replace them all."
Minhaj al-Qasidin.
Al-Ghazali, despite being a scholar, was not an expert in the field of hadith and thus the hadith narrations contained in his book were scrutinized. Hadith experts like Ibn al-Jawzi and Ibn al-Qudamah al-Maqdisi researched and sorted out the hadith narrations contained in the book on the basis of their authenticities. They then wrote the "Minhaj-al-Qasidin" and its overview called "Mukhtasar". 
The book was then carefully reworked by Ibn al Jawzi (597 AH) and the result of his work was named "Minhaj al-Qāsidīn wa Mufīd al-Shādiqīn". Ibn al-Jawzi's efforts in rewriting the book is considered important and while he had similarities with Al-Ghazali in terms of mastery in mysticism, he also had the superiority of expertise in the knowledge of the hadiths. The reworking by Ibn al-Jawzi focused on the re-examination of the existing hadiths, elimination of weak and disputed hadiths and their replacement with the authentic and sound ones so that the integrity of the book was not compromised. 
Minhaj al-Qasidin was a fairly thick book and it was summarized in the form of Mukhtasar by Imam Ibn Qudamah. Whenever Ibn al Jawzi focused on the study of hadith, he found the "Mukhtasar" book in line with its name, aiming at summarizing and making the essence of the previous book to be more concise, organized, and easy to understand. It also added additional notes so that it may become an easy book for students to read. Ibn Qudamah remarked that whenever he read Ibn al Jawzi's Minhajul Qasidin, he felt that this book was very useful for society, so he would read it again in order to absorb the deeper meaning for the second time. He said that his admiration for the book grew such that he also added some important missing topics that were readily available in other prominent books of his time with additional notes such as hadith and commentary.