What is also interesting is Naskh (abrogation). This is when there are contradictions found in the Quran, Sunnah, Haddith that the newest aya (verse) replaces the older aya(s).
For instance, there are ayas in the Quran that shows alcohol was not forbidden for Muslims, but later an aya was written in which it was said that it was forbidden, so the newest aya makes the older no longer relevant.
for the example below, note that Quran is not chronological, but organized in terms of length. So the aya from chapter 3 can replace the aya from chapter 5 and 2.
Surah 2:62 (some claim this is abrogated by Surah 3:85 below)
Those who believe (in the Quran) and those who follow the Jewish (scriptures) and the Christians and the Sabians, - Any who believe in Allah and the Last Day, and work righteousness, shall have their reward with their Lord: on them shall be no fear, nor shall they grieve.
Surah 5:69 (some claim this is also abrogated by Surah 3:85 below)
If only they had stood fast by the Law, the Gospel, and all the revelation that was sent to them from their Lord, they would have enjoyed happiness from every side. There is from among them a party on the right course : but many of them follow a course that is evil.
Surah 3:85
If anyone desires a religion other than Islam (submission to God), never will it be accepted of him; and in the Hereafter he will be in the ranks of those who have lost (All spiritual good).
So we see a complete contradiction here. Will only Muslims be rewared for there faith or also Christians and Jews? Because of Naskh, little to no attention is paid to verses that speak positively about faiths other than Islam, or to the many many other contradictions in the Quran. Smart solution!