Basically Quran is guidance of Allah for anyone who read it and believe in it as word of God. And yes, indeed Quran's guidance is basically all about establishing peace, harmony and tolerance, but all of it requires character, so either your character is built by your parents, society or you read Quran /Bible /Other and correct your self accordingly.
Just a little back ground and if i'm not wrong, Quran was compiled in it's current form by the companions of messenger, after his death.
An effort lead by the Khalifa Umer, until than it was memorized by hundreds of Muslims who took part in the compilation effort, every verse was reconfirmed from many different persons, before getting approved, but still the order of verses is not same as it was revealed by angle Gabrial.
Generally speaking, Quran draws an out line for behaviour, acting upon which a peaceful society can be established.
One can establish a peaceful society without reading Quran but to have a title of Muslim, one needs to believe in God almighty and all knowing.
Quran in it's existing form is message of God almighty, brought to Mohammad (p.b.u.h.) by angle Jibrail (Gabrial).
In similar way, who followed guidance of same one God through earlier messenger like Isa, Musa and more were also Muslims as they also believed in the message of God and God almighty. Word Islam means to submit to guidance of God.
I don't know the history of Bible's compilation, but it certainly was limited revelation for a limited geography and time, and today it does not does not exists in it's original language. What followed centuries after was another but final round of revelations, today exist in form of Quran.
Irrespective to the different versions, Quran and Bible are largely similar in guidance. Since i have not read bible more than few stories in my childhood, i guess Quran address additional subjects and is believed to be complete and all what ever was suppose to come to mankind as an extra guidance, beyond what is already constructed and programmed in his creation. So that there's no excuse left on the day of judgment, where ultimate justice will be served, considering all circumstances and time, wherein each human being lived.
Only Arabs can read and understand Quranic verses, unfortunately non Arab speakers at best can read but can't understand, we are limited to translation.
There is a chapter about messenger Isa about Mariam and Isa is mentioned therein and surely at other locations. Once i came across a research work by a Egyptian scholar (Author:
Shawqi Abu Khalil), which lists all messengers of God mentioned in Quran and exactly where are they mentioned.
Book is called 'Atlas of Quran' obviously it details about geography as well.
It's true that so called Islamic revolution of Iran was one of the biggest mischief ever in Islamic history. Since than they started mixing history, politics and even culture with religion. May be there's alteration in Quran as well, but it's easy to misguide in regions, who can't read or write Arabic.
Therefore the concept of Imam emerged in such far regions, job of Imams was to learn Arabic and guide us no Arabic speakers, quite naturally we gave too much respect and trust to such person, which was than exploited by intelligence agencies of non Islamic states. In Pakistan we have apprehended many Indians of Hindu belief working as Imams in mosques of Pakistan, where they preached all sort of nonsense as Islam.
However in today's world, job of Imam is not required and we can have translations available and can compare, word by word. However learned scholars can always help explain same subject in detail.