In Islam, the Quran is the most holy of all books. It is the source of their religious practice and devotion. Muhammed claimed that the Quran (Koran) was revealed to him through the work of the Archangel Gabriel. It is supposed to be an exact representation of the heavenly version of the Tablet Heaven (Surah 85:21-22) and is without error (Surah 4:82). It consists of 114 chapters, called surahs that are arranged roughly from largest to smallest. each chapter consists of versus called ayahs. According to Islam, of the 114 chapters, 86 were given to Muhammad while he was in Mecca. The other 28 were revealed in Medina.
Muhammad claimed that Gabriel ordered him to recite and memorize the verse. These were written down on various materials (wood, parchment, bones, etc.) by Mohammed's followers. The Quran is supposed to confirm what came before it (Surah 3:3), be free from error (Surah 4:82), and is true guidance (Surah 2:2-5). It's laws and wisdom are supposed to be perfect. However, the Quran is far from perfect. For example, it teaches a man's seed comes from his chest (Surah 86:5-7) and that Mary was the sister of Aaron (Surah 19:27-28). Is it from God? How can it be if it is blatantly wrong on various facts.
There are many topics covered in the Quran including abrogation, Adam, Allah, animal sacrifice, the Bible, Christians, denial of the crucifixion of Christ, forgiveness, Holy Spirit, Jesus, marriage, Mary, Mohammed, ransom, reproduction, salvation, etc. It speaks a lot about governmental systems as it relates to Muslims as well as admonition for Muslims to seek to dominate the world and even kill unbelievers (Surah 9:29). Furthermore, the Cron itself says that it is a guide to mankind (Surah 2:185), that is free from error (Surah 4:82), that its laws are true and street (Surah 98:3), and that it originated from Allah (Surah 10:37).
Muslims routinely claim that it is full of miraculous information about the human body, nature, etc. But these claims are often open to exaggerated interpretations where texts are twisted in order to support a pre-supposed conclusion. Native speakers say the Quran is in beautiful Arabic and Muslims practice memorizing large portions of its pros. Someone who has memorized the entire Quran is called a hafiz. Therefore, it is recited and even chanted on a regular basis from mosques as many people have experienced in the call to prayer which occurs five times a day. In all of Islam, no miraculous events are recorded. Instead, the Quran itself is supposed to be a miracle.
The Quran has many biblical themes in it though they are often distorted. It mentions many biblical characters such as Adam, Noah, Moses, David, Jesus, etc., and has biblically related themes such as salvation and cosmology. In order for Muslims to understand what the Quran teaches they often refer to tafsir, which is exegetical commentary on the Quran. There are different tafsirs available today in English.
The Quran was not gathered together during the lifetime of Mohammed who died in 632 A.D. Instead, it was assembled later. The first Caliph Abu Bakr is also the first one to try and collect the Quranic verses that were scattered among the people and had been memorized or written down by the followers of Islam. Since people who had memorized portions or the totality the Quran were dying, it was necessary to preserve the Quran. So the order was sent out to collect scraps, bone fragments, writings, whatever might have been in assembled. However, there was a problem because there were differences in the Quran. Caliph Uthman (d. 656) is the one who assembled a particular set of Quranic versus and had the rest of the copies destroyed. This the Quran that is used today.