The Quran is God’s greatest gift to humanity it is a book like no other. In the second verse of the second chapter of the Quran, God describes the Quran by calling it a book whereof there is no doubt, a guidance to those who are pious, righteous, and fear God. (Quran 2:2)
The Quran is core to Islam. Believing in it is a requirement. One who does not believe in the Quran, in its entirety, cannot claim to be a Muslim.
“The Messenger (Muhammad) believes in what has been sent down to him from his Lord, and (so do) the believers. Each one believes in God, His Angels, His Books, and His Messengers. (They say,) ‘We make no distinction between one another of His Messengers’ — and they say, ‘We hear, and we obey. (We seek) Your forgiveness, our Lord, and to You is the return (of all)’.” (Quran 2:285)