As for the present structure of Al Qur'an, we can say that it is reasonable.
For example:
Verse 2: 23 says: "If you are in doubt regarding what We have sent down, then bring a sura of the like thereof..."
Now if you look at the present structure of the Book, we find a small complete sura Al Fathiha in the Book before the 2nd sura wherein is this verse.
Verse 11: 13 says: "... then bring ten similar (but) forged suras..."
Now if we look at the Quran as it is today, we will see that before this verse which is in the 11th sura, we have obviously ten, and only ten divinely revealed suras.
For example:
Verse 2: 23 says: "If you are in doubt regarding what We have sent down, then bring a sura of the like thereof..."
Now if you look at the present structure of the Book, we find a small complete sura Al Fathiha in the Book before the 2nd sura wherein is this verse.
Verse 11: 13 says: "... then bring ten similar (but) forged suras..."
Now if we look at the Quran as it is today, we will see that before this verse which is in the 11th sura, we have obviously ten, and only ten divinely revealed suras.