From Wikipedia

Decoding The Past: Secrets Of The Koran

Part Two

Muslims regard the Qur’an as the main miracle of Muhammad, as proof of his prophethood, and as the culmination of a series of divine messages. These started, according to Islamic belief, with the messages revealed to Adam, regarded in Islam as the first prophet, and continued with the Suhuf Ibrahim (Scrolls of Abraham), the Tawrat (Torah or Pentateuch), the Zabur (Tehillim or Book of Psalms), and the Injeel (Christian Gospel). The Qur'an assumes familiarity with major narratives recounted in Jewish and Christian scriptures, summarizing some, dwelling at length on others, and, in some cases, presenting alternative accounts and interpretations of events. The Qur'an describes itself as a book of guidance, rarely offering detailed accounts of specific historical events, and often emphasizing the moral significance of an event over its narrative sequence.

Islamic tradition relates that during one of Muhammad's isolated retreats to the mountains, he received his first revelation in the Cave of Hira. Thereafter, he received revelations over a period of twenty-three years. According to hadith and Muslim history, after Muhammad emigrated to Medina and formed an independent Muslim community, he ordered a considerable number of the companions (sahaba) to recite the Qur’an and to learn and teach the laws which were being revealed daily. Companions who engaged in the recitation of the Qur’an were called qurra'. Since most sahaba were unable to read or write, they were ordered to learn from the prisoners-of-war the simple writing of the time. Thus a group of sahaba gradually became literate. As it was initially spoken, the Qur’an was recorded on tablets, bones and the wide, flat ends of date palm fronds. Most chapters were in use amongst early Muslims since they are mentioned in numerous sayings by both Sunni and Shia sources, relating Muhammad's use of the Qur'an as a call to Islam, the making of prayer and the manner of recitation. However, the Qur’an did not exist in book form at the time of Muhammad's death in 632.