There are different views among different school of thoughts among Non muslims on who authored the Qur;an, This book address all the questions you might have.when God Almighty decided to create Mankind, he didnt intend to leave them without guidance. to achieve this feat, Allah had appointed various prophets and Messengers together with various divine books throughout past generations and present generations to serve as a manual to all mankind so that they dont derail from the purpose of their creation.