The Holy Qur'an is a Sacred Book. It is the speech of God that was sent down to all mankind for the sole purpose of guiding them to the straight path of acknowledging God's Oneness and dedicating their acts of worship exclusively to Him.

Verily, this Qur'an guides to that which is most just and right and gives glad tidings to the believers who work deeds of righteousness, that they shall have a great reward (in Paradise).

(Surah Al-Isra:9)

God revealed the Qur'an to Prophet Muhammad, through the Angle Gabriel, in stages as circumstances warranted over a period of twenty three years. Throughout its 114 Chapters (Surahs) are discussed issues of belief, the proof of God's existence and the Day of Judgment and Resurrection. The Qur'an also contains many scientific facts, stories of the prophets and information on issues of law, society and governance. 

All the prophets, including the Prophet Muhammad, have preached the same message that came in all of the sacred books concerning the Oneness of God

It is He Who has sent down the Book (the Qur'an) to you (O Muhammad) with truth, confirming what came before it. And He sent down the Torah and the Gospel aforetime as a guidance to mankind. And He sent down (this Qur'an as) the Criterion (of judgment between right and wrong). Truly, those who disbelieve in the revealed Verses of Allah, for them there is a severe torment; and Allah is All-Mighty, All-Able of Retribution.

(Surah Al-Imran:3-4)