If you want extensive proof, you would have to read one or both of the following books.
Cosmic Codes
Creator Beyond Time and Space
For me, proof of God's existence as well as the Bible being the Word of God can be proved through the vehicle of prophecy. To see the evidence of this, we must first establish the fact that God is a spirit who dwells outside of our physical time domain--that is, in eternity. In the Bible, God describes Himself in Isaiah 57:15,
"For thus says the High and Lofty One Who inhabits eternity, whose name is Holy: 'I dwell in the high and holy place, with him who has a contrite and humble spirit.'"
If God dwells in the realm of eternity as the Bible states, then He must be able to declare future events as if they had happened in the past. We who live in the physical restraints of time and space have the disadvantage of seeing the world according to a timeline. But God sees the past and the future as one complete picture.
"Remember the former things of old, for I am God, and there is no other; I am God, and there is none like Me, declaring the end from the beginning, and from ancient times things that are not yet done, saying, 'My counsel shall stand, and I will do all My pleasure,'" Isaiah 46:9-10
So through the vehicle of prophecy, God throws down the gauntlet to all the other "holy books" and all the other "gods" that dare to claim the title. The God of the Bible challenged in Isaiah 41:22-23,
"Let them bring forth and show us what will happen; let them show the former things, what they were, that we may consider them, and know the latter end of them; or declare to us things to come. Show the things that are to come hereafter, that we may know that you are gods; yes, do good or do evil, that we may be dismayed and see it together."
OK, there is the challenge from the God of the Bible. No other book contains prophecy that has been fulfilled with accuracy. Some would say that others twist scripture interpretation to make prophecy "appear" to be fulfilled. A silly notion, seeing that so many of these prophecies (that were fulfilled to the letter) were found among the Dead Sea Scrolls--written many years before fulfillment. I have written one study based on one chapter in Daniel. In it can be found 16 in-depth prophecies regarding the rise of Alexander the Great and the subsequent rule of his generals afterward. I have paralleled the prophecy with the fulfillment from historic literature. You can find the study here.
This study only covers one chapter. There are hundreds more regarding the coming of the Messiah, the calling of Cyrus the Mead by name to allow the rebuilding of the temple in Jerusalem, and the re-establishment of the nation of Israel.
Note that an event like this has never happened before in all of history. In fact, Robert Anderson who was the inspector for Scotland Yard (who caught Jack the Ripper) took the book of Daniel as providing the date Messiah was to come. His incredible calculations pinpointed the DAY Jesus rode in to Jerusalem. For this, he was knighted by Queen Victoria and became Sir Robert Anderson. However, he read other prophesies regarding Israel becoming a nation again and thought that this was WAY too preposterous. No nation, after being conquered and scattered, EVER returned again to form a nation and a people. So it must have had some "allegorical" meaning to it. Well, in 1948, Sir Robert Anderson was proven wrong. Sir Robert Anderson believed the Bible, but his doubt in a wild claim such as Israel becoming a nation was too much for him. THAT is how accurate prophecy is. Before the fulfillment took place, Anderson assumed it was wrong (having lived in the Victorian era pre 1948). He twisted nothing, but assumed it was something else entirely.
Isaiah 34:16
"Search from the book of the LORD, and read: Not one of these shall fail; Not one shall lack her mate. For My mouth has commanded it, and His Spirit has gathered them."
2 Peter 1:16-21 (condensed)
For we did not follow cunningly devised fables when we made known to you the power and coming of our Lord Jesus Christ, but were eyewitnesses of His majesty...and so we have the prophetic word confirmed, which you do well to heed as a light that shines in a dark place...for prophecy never came by the will of man, but holy men of God spoke as they were moved by the Holy Spirit.
