The basis for the Bible being the Word of God is prophecy. In each of the approximately 6,000 years of human history that prophecy has been fulfilled, the conditions for its fulfillment were first met. Over a period of approximately 1700 years, the Bible consistently records the fulfillment of prophecies inspired by God's anointed prophets concerning the destruction of the nation of Israel; the first coming of Jesus Christ; the restoration of the nation of Israel; the second coming of Jesus Christ; and the judgment of Satan. The reestablishment of the state of Israel in 1948 after its destruction by the Roman Empire in 70 A.D. is a sign of the imminent fulfillment of the prophecies of Jesus Christ's return.
If God revealed things in the Bible that humans must know, He would not have written things that are not understood. I don't think there is any prophecy that cannot be understood if one understands the concept of purposive inevitability that prophecy must be fulfilled as such.