The Koran claims that it is the exact, precise words of the only god of the universe. It claims to be perfect, complete, final, eternal, universal and is without a single error. The story of the Koran is that the archangel Gabriel spoke to Mohammed and delivered the exact words of Allah. The Koran is true by its own assertion, or because it says that it is true. The transmission of the Koran unfolded over 23 years.
The Koran is actually two books, the early Koran written in Mecca and a later Koran written in Medina, The Meccan Koran is religious, but the Medinan Koran is very political, legal and devotes nearly a quarter of its words to jihad.
The summary message of the Meccan Koran is that Mohammed is the prophet of Allah and humanity must submit to Allah. The message of the Medinan Koran is that if you do not believe that Mohammed is the prophet of Allah, you can be harmed.
Readers of the Koran find it to be difficult and contradictory. One of the key principles of the Koran is that if two verses contradict each other, the later verse is stronger and better than the earlier verse. The process of determining which verse is stronger or better is defined as abrogation. The problem with this is that the Koran is not arranged in any kind of chronological order, so knowing which verse is better is confusing. The Koran is highly repetitive, with stories being repeated many times. Most of the stories are incomplete and details change with repetition.