Keltoi, there are two opinions on this amongst the scholars, one is that the meanings of the qur'an are from Allah, the words from the prophet, the other is that both meanings and words are from Allah. doesn't make much difference either way, no one claimed that Allah 'wrote' books. straw man..
on subject, we 'believe' the qur'an is true, faith and reason are both in play here, if the qur'an is coherent-no contradictions-, and makes no claims that could be falsified by science, and the moral commands and world view etc there are sound, and have benefits then it's 'true'. the bible and Torah specifically have been tampered with by men 'inspired' by God, many other 'bibles' existed, why the current ones and not the others, not to mention other obvious indicators of it not being 'true' anymore.