Hadiths and deceivers.

[Angrboda]

How does belief in design lead to belief in a specific book?  You're using design as a sign of confirmation after the fact of already having taken the leap to believe in the Quran, but you believed in that specific book first.  How does design uniquely point to this book rather than that one?

No; the "leap" is the step taken after the observation takes place.
First, you notice something strange about the world and about the universe.
Second, you begin to search for explanations. One of the explanations is stated in the Quran.

There are so many explanations out there, rejecting all explanations is what you are: atheism.

Personally; I take the explanation in the Quran for the design to be a perfect sign of confirmation: the design led me to search, the found explanation led me to believe that the design served a purpose, both are dependent on each other.

So why aren't you then a Christian? Or a Jew? Or a Hindu? These all have creation stories. What you are saying doesn't make sense. On top of that, creation stories are so common, it's like saying that because the bible mentions Egypt, a real place, then the rest of it is true. Design gets you to a generic god; to go further and conclude the God of the Quran, you have to add something that isn't there.