The Quran is the backbone of Islam. On this Sacred Book of Allaah depends the Islamic call, state, society and the civilisation of the Muslim world. It is the last Divine revelation, which was sent down to Prophet Muhammad , the last and final of all Prophets, may Allaah exalt their mention. His task was to convey the message of worshipping the One God, Allaah, without ascribing any partners to Him. The Noble Quran, which is the source of guidance and mercy to mankind, is divided into one hundred and fourteen (114) Soorahs (chapters) of varying lengths. Ninety-three chapters were revealed in Makkah, while the remaining twenty-one were revealed in Madeenah.
The first revelation that the Prophet received was Soorat Al-'Alaq, which was in Makkah where Soorat An-Najm was to later became the first to be recited openly to the people. In Madeenah, Soorat Al-Mutaffifeen was the first one revealed after the Hijrah (migration). The Prophet had to flee to Madeenah to save his own life and the lives of his followers, upon the command of Allaah.
The last verse sent down to the Prophet was the saying of Allaah which means: “…This day I have perfected for you your religion and completed My favour upon you and have approved for you Islam as religion...” [Quran: 5:3]
Some chapters in the Quran focus on the call to Islam as guidance for humanity. They focus upon monotheism and the fight against polytheism and idolatry. Thus, stress is laid on all that is related to faith. In other chapters, attention is given to legislation, acts of worship, relationships among people and the laws that regulate matters within the Muslim community, government, and family.
A number of chapters inform about Resurrection, the Hereafter and the unseen; others relate the stories of various prophets and their calls to their people to return to Allaah. We see how the previous nations were severely punished when they disobeyed Allaah and denied the messages of previous prophets, may Allaah exalt their mention.
In addition, several chapters focus on the story of creation and the development of human life. In fact, Makkan revelations made the Muslims' faith in Allaah firmly established. On the other hand, Madeenan revelations were meant to translate the faith into action and give details of the Divine Law.
Allaah will forever preserve the Quran against all attempts to destroy or corrupt it. Being guarded by Allaah, it will always remain pure. There does not exist a single copy with any variation from the recognised text.
Any attempt of alteration has resulted in failure.
Upon the command of the Prophet his Companions would write down what was revealed of the Noble Quran. They used, for this purpose, palm branches stripped of leaves, parchments, shoulder bones, stone tablets, etc. About forty people were involved in this task. Among them was Zayd Ibn Thaabit who showed his work to the Prophet . Thus, the Quran was correctly arranged during the Prophet’s life, but it was not yet compiled into one book. In the meantime, most of the Prophet’s Companions memorised the Quran.
When Abu Bakr became Caliph after the Prophet died, a large number of the Companions were killed during the War of Apostasy. 'Umar Ibn Al-Khattaab went to the Caliph and discussed the idea of compiling the Quran into one volume. He was disturbed, as most of those who memorised it had died. Then, Abu Bakr called for Zayd and commissioned him to collect the Quran into one book, which became known as the 'Mus-haf.'
After Zayd accomplished this great task and organized the Quran into one book, he submitted the precious collection to Abu Bakr who kept it in his possession until the end of his life. During the caliphate of 'Umar it was kept with his daughter Hafsah who was also a wife of the Prophet . During the Caliphate of 'Uthmaan Islam reached many countries, and readers began to recite the Quran in different ways (dialects). 'Uthmaan then had various copies made and sent them out to the different Muslim lands, lest these dialects would cause alterations to the Quran, and kept the original copy with Hafsah . Thus, the Quran remained preserved and the Caliph was very much pleased with his achievement. Today, every copy of the Quran conforms with the standard copy of 'Uthmaan . In fact, Muslims over the ages excelled in producing the best manuscripts of the Noble Quran in the most wonderful handwriting. With the introduction of printing, more and more editions of the Noble Quran became available all over the world. Source : http://www.islamweb.net/