Hi, and thanks for the question.
The best way to describe the bible is that it is God’s chosen way to reveal himself (and his Son) to us. That is not to say that God is limited to this method alone - he can choose to reveal himself to us in any number of ways and has through the ages. But he has PROMISED to reveal himself to us through the scriptures. So my answer to your question is that while the bible might not be the only way to know Jesus, it is certainly the best and most effective way. Let me explain.
When Jesus walked this earth, a complete ‘Bible’ (as we know it) didn’t exist. People came face to face with the Lord Jesus himself. However the Old Testament (OT), or Hebrew Tanakh did exist. Jesus gives his approval to the Tanakh by saying, ‘everything written about me in the Law, the Prophets and the Psalms, must find its fulfillment’ (Luke 24:44). Since the Hebrew Tanakh was in three sections (with these headings) and existed in this form at the time of Jesus, he is actually approving of all of them. In other words, Jesus didn’t just appear out of nowhere and say ‘I’m your Lord and Saviour, the Son of God, believe in me’. He comes as the fulfillment of expectations set up by God himself in the Tanakh. In fact, Jesus says that the Hebrew Scriptures are one of the most powerful testimonies to himself (John 5:36-40). And Jesus is constantly quoting Scripture to prove that he is the long awaited Christ, the Saviour of the world. So at the beginning of Christianity, both Jesus himself and the Apostle Paul appeal to the Scriptures to have true and certain knowledge about Jesus (see Acts 17:2, 17:11).
Now it is true that unschooled fisherman (Acts 4:13) came to know Christ purely through interaction with him. But they were all Jews and even unschooled Jews were saturated with the Scriptures through the Jewish Synagogue (this was the case, even if they were illiterate, because the Scriptures were recited orally and sung. It was an oral culture). The Synagogue was the cultural hub of Jewish society, so people would go there throughout the week, not just on the Sabbath. The unschooled fisherman, Peter, still commends the prophetic Scriptures, to study and live by (2 Peter 1:19-21).
So Jesus and the early Apostles grounded much of their teaching on the Hebrew Scriptures. So how did these Scriptures come to be written down? Was it a man-made invention, or ordained by God? Even though the Ancient culture was an oral one, from a very early time, God commanded his words to be written down. This is because his dealings with Israel revealed who he was and what kind of relationship they could have with him. It was God’s command that ordinary Jews learn his words and write them everywhere as a constant reminder (Deut. 11:18-21). God also commanded his words to be written down so they would be preserved for future generations - the leaders and kings were to meditate on it (Exodus 34:27; Deut. 17:14-20; Joshua 1:8).
I hope I have shown how important the Hebrew Scriptures are. But let’s imagine that someone in Jesus’ time understood the message of Jesus without the Scriptures. All well and good. But what about the great majority of people who lived after Jesus died and was raised again? How will they come to know Jesus since he isn’t physically present anymore? I hope to show that Jesus himself made provisions for the writing down of the New Testament (NT) Scriptures, and so commends to us the whole Bible as the best way to know him:
1) Jesus is very clear that he will not be physically present forever (John 13:33), and so there needs to be another way for people to come to know him. The method that Jesus chooses is his Apostles (Luke 24:45-58; John 15:26-27). But the disciples are not able merely to recite what they heard from Jesus. They need the power of the Holy Spirit to teach them all things and make them able to witness to Jesus (Luke 24:49; John 16:12-14 & 17:20-21). The reason the NT is the best way to know Jesus, is because it is the words of the Apostles themselves written down.
2) The NT was written down so that after the Apostles had died, future generations would be able to have a reliable witness to Jesus’ life and teachings. Is this a human invention or was it ordained by God? Jesus refers to those who will write down his message as a scribe for the kingdom of heaven. He says that they will need to testify to Jesus by referring to the old treasures (Old Testament), and the new (Jesus’ life and teachings), in Matthew 13:51-52.
3) The Apostles realised that they need to write things down as they approached their own death (2 Peter 1:12-15). They therefore made provisions for faithful men to transmit this message from generation to generation (2 Timothy 2:1-2). All Scripture is breathed out by God (i.e inspired by him), and is the God-ordained method to know Christ (2 Tim 3:14-16). At the end of the New Testament, there is a stern warning not to add anything from the this book or take away anything from it (Revelation 22:18-19). This can be applied to the whole New Testament, since any writings written after this time would not be as authoritative since they don’t have Apostolic approval, and so don’t have approval from Jesus himself.
But what about the person who sees a vision of Jesus and comes to know him this way? Of course this is possible and has happened to people, including a man called Sadhu Sundar Singh (http://en.wikipedia.org/wiki/Sundar_Singh). But this is very rare, and after this visionary experience, they always grow in their knowledge and love of Jesus through the Scriptures. Your concern might be that not everyone can read, or not everyone has the Scriptures. But you can take in the Scriptures orally, and the Bible society has made Scripture available orally to many remote communities of people in their own language (through an mp3-type device). What I’m saying is that this method is the way God has promised he will reveal himself to us. Otherwise we would be demanding a personal vision of Jesus to each and every one of us, which God has not promised in the Scriptures. In addition, other ways of knowing Jesus are not as trustworthy, since they have not been promised by God.
In summary, God has always made sure that people have access to his word. And his Word is ultimately Jesus himself, who makes himself known through the Apostles, the New Testament. If you are concerned that the Bible is merely an intellectual document, be assured that through the power of the Holy Spirit, it becomes a living and active Word that engages our heart, mind and soul.
When you accept the teaching of Jesus, we accept Jesus himself. As he says, “If anyone loves me, he will obey my teaching. My Father will love him, and we will come to him and make our home with him.”
May you be blessed in your knowledge of Christ.