The Koran and the Bible are books written by people for the purpose of a certain benefit for them, so there can not be truth in them.
Actually, this statement is false. You can compare many aspects of life with what is written in the Bible, or the Koran, and see that the books are accurate to some extent. When the accuracy is sufficient for you in the areas you understand are true, you might assume that the whole book is true.
Partially there is the right information, but it is then specifically introduced there so that people think that this is true. But many do not want to be slaves to religion and face the truth.
Everybody is a slave to religion, even if it is only his own personal religion. Check the definition of religion, http://www.dictionary.com/browse/religion?s=t. Some people tight in this forum have been shown to have a religion of non-religion, because they fight against the idea of having religion. Check out the thread, "Why do Atheists hate Religion ?," at https://bitcointalk.org/index.php?topic=1054513.0.