There are three main reasons why it should be glaringly obvious the quran is fabrication, made up by Muhammad, and not the words of God.
Firstly it is filled with myths from the bible and from Arabic mythology, and these myths are presented as true history when they are clearly unrealistic.
Secondly it is filled with simplistic statements that make it plain Muhammad had no special knowledge, like the sun orbits the earth and goes to a resting place, and the earth is flat.
But these verses are disputed by Islamic scholars who try make them seem to mean something more complex.
Thirdly the God the quran describes is incompetent and blunders his way along, destroying and killing people, and then burns them with terrible tortures for all eternity, and this is not worthy of God.
Muslims will say the bible has the same hell, but it is obvious the real point of the quran is to scare people into obeying Muhammad for fear of punishment by God, and the quran says many times " fear Allah and obey the messenger".
Meaning obey Muhammad or else, and that is the real meaning of the quran.
I already know the main arguments muslims will put forward, and one is you cannot understand the quran unless you can read arabic, but I say the meaning of much of it is obvious even in English. Then muslims will say you take verses out of context, but the quran is a rambling haphazard set of verses which often have no continuity to them, and it makes statements then jumps to another subject. Just like you would expect a clever Arab to speak if he was telling stories from the bible and making things up. Sura 12 is the most obvious piece of plagiarism, as it is a half remembered tale that makes no sense unless you have read the bible.
So I intend to take the quran apart on this thread and show some of what is wrong with it.