All religions claim that their scripture is the divine word of God. Hence, there is no point of investigating that, right? WRONG!
Here is a quite interesting but less-known piece of information. Do you know that the Quran is the only book that speaks in the first person of God? All other scripture only talk about God. If a book is the word of God, why wouldn’t it say “God created us,” and so on, instead of “We created you”?
Actually, there is one exception here, the Torah. A part of the Torah is written in the first person of God. But here is another interesting piece of info. The Quran says:
“Say (Muhammad): “Produce, then, [another] revelation from God which would offer better guidance than either of these two [The Torah and the Quran, and] I shall follow it, if you speak the truth!. And since they cannot respond to this thy challenge, know that they are following only their own likes and dislikes: and who could be more astray than he who follows [but] his own likes and dislikes without any guidance from God? Verily, God does not grace with His guidance people who are given to evildoing!” (28:49-50).
When the Quran challenged humanity to show another book from God, it didn’t say one other than the Quran; it said other than the Quran and the Torah, since they both are from the Creator, at least originally in the case of the Torah.
This is surely is not a sufficient evidence for a book to be the word of God, but it is a starter and an indication. It narrows down the options a great deal :)