The Bible is a big deal to Christians because, for us, it is the primary way that God has chosen to make Himself and His salvation known to the world. To say it more carefully, God has revealed His character and saving work perfectly through the incarnation of His Son as recorded in the Scriptures.
With that in mind, it shouldn’t be difficult to see how important knowing the Bible is to Christianity. Reading the Bible is the food and drink of true Christians, but they do a lot more with the Bible than simply read it. I believe the London Baptist Confession (1689) gives a good, concise summary of the primary things Christians do with their Bibles.
By this faith Christians believe to be true everything revealed in the Word, recognizing it as the authority of God himself. (Acts 24:14)
They also perceive that the Word is more excellent than every other writing and everything else in the world (Psalm 27:7-10; 119:72), because it displays the glory of God in his attributes, the excellence of Christ in his nature and offices, and the power and fullness of the Holy Spirit in his activities and operations. So they are enabled to entrust their souls to the truth believed (2 Timothy 1:12).
They respond differently according to the content of each particular passage—obeying the commands (John 14:14), trembling at the threatenings (Isaiah 66:2), and embracing the promises of God for this life and the one to come (Hebrews 11:13). (XIV:II).
Christians believe the Bible to be true, perceive the Bible as the most excellent writing ever penned, and respond to the Bible in faith and obedience.