One of the characteristics of the divine book is its language.
As the Qur’an has preserved its language as it was revealed to the Prophet, it maintains its status as the divine book. Otherwise, it could not be deemed a divine book. The divine books that have been translated into other languages cannot be called directly divine books. For example, the Qur’an translated into Turkish cannot be called the Qur’an, but rather the Turkish translation of the Qur’an.
It is clear that the Qur’an, the last divine book, has preserved its language as revealed to Prophet Muhammad. It is the only book that has preserved the status of divine book in terms of linguistics.
Another characteristic of the divine book is its syntax. 
To maintain the syntax is to preserve the places and the word order that was determined by Allah. Let us look at different copies of the Qur’an. Beginning from the Mother Qur’an, written down in the era of Prophet Abu Bakr, let us take historical copies, including those copied by Prophet Uthman, one of which is exhibited in the Hermitage in St. Petersburg with the one being exhibited in Topkapi Palace, and contemporary copies printed in different countries. We can see that they all begin with Surah Fatiha and end with Surah An Nas, and the syntax is the same in all, that is it is the syntax determined by Allah.
The Qur’an is the only divine book in terms of lyrical structure, as well. The most important characteristic of the divine book is that it should belong to only Allah and contain no contribution from anyone other than Allah. If the words of the prophets or other people are added to divine books, they will no longer be divine and cannot be regarded as the main source of their religions. 
Prophet Muhammad, the last prophet, prohibited his words from being written, allowing only the verses of the Qur’an to be written so that the Qur’an would not be changed.  His words are known as Hadith and have not been added to the Qur’an. Saying “Amen” after reciting Surah Al-Fatiha is the practice of the Prophet, but this word has not been added to the Qur'an, because it is not the word of Allah, but the word of the Prophet.