The Irony Of 'word Of God', A Question To Believers

Here's a question I'm asking in good faith to believers, how do you differentiate between the word of God and the word of man?

Throughout civilization, a vast library of literature spanning aeons, cultures and empires have been written all claiming to be inspired of and containing the will and message of god. Most have been lost in the passage of time, but quite a few remains in the modern times and continues to guide and dictate the daily conduct of millions across the globe. One funny thing about these writings is that despite the bold claim to be the words of a supreme deity, they were all written, compiled by and continues to be propagated by men. God it seems is unable to speak and spread his own ideas. That these writing seems to contradict one another doesn't help matters either. How does a sincere seeker of God arrive to a rational conclusion of what is God's word and what isn't? How do you separate the mind of God from the fantasies, ideas, imaginations and bias of the writers, compilers, editors and proselytes of these books? Is there a standard of what is God's word and what isn't and if there is then who laid down these standards and on what grounds were they laid down??
But most importantly, what is the word of God??