Author: Allah Subhanahu wa-ta'ala
The Quran is a Divine Miracle of Literature [Prophesy - Science - Warnings - Wisdom - Truths] and it has been Preserved 100% In the Original Language - for over 1,400 years!
Humanity has received Divine Guidance only through two channels:
The Word of Almighty God ("Allah" [in Arabic]) [scriptures, Bible, Psalms, etc.]
The Prophets sent by the Allah to communicate His Will to mankind
These two things have always been going together, hand in hand.
More important though, there were at that time, tens of thousands of his companions ("sahabi" in Arabic) who memorized the complete Quran from the instruction of the prophet Muhammad (peace be upon him). Even the prophet himself (peace be upon him) used to recite it with angel Gabriel once a year and in the last year of his life he recited it two times just before the month in which he died.
Next, the leader who came after the prophet Muhammad (peace be upon him) (Abu Bakr) entrusted the collection of the Quran to be written in one volume by one of the Prophet's scribe, Zaid Ibn Thabit. He kept it till his death. Then the next leader, Umar and after him to his daughter, Hafsa who had been one of the wives of Prophet Muhammad (peace be upon him).
Then from the original text which now resides in Topkope Museum, in Istanbul, Turkey, the next leader, Uthman prepared several other exact duplications and sent them to various Muslim territories such as; Uzbekistan and Turkey and other places. These scriptures are still in museums there and one has found its way to a museum in England as well. All of them are exactly the same. Today many of the Muslims from these areas are still memorizing the Quran.
The Quran was so meticulously preserved because it is the Book of Guidance for all of humanity for all times. That is why it does not address just the Arabs, in whose language it was revealed. In fact Arabs today do not comprise more than 13% of the Today of Muslims in the world today.