I’ve been asked how I know the Bible is true, and before I returned to the Lord, I went through a whole lot of investigating (especially to pull together science and the Bible) before deciding I could believe it 100%. I would encourage anyone with this question to also do research and especially recommend Answers in Genesis as a great resource regarding the Creation/Evolution debate. But here’s what it really comes down to:
Jesus promised that His sheep will hear His voice (John 10) and would be able to discern true teaching from false teaching (John 7:14-18). I do hear His voice, and I have discerned that the protestant Bible is inspired by God (though I like some translations better than others, and a couple, I absolutely couldn’t recommend).
I have not, as a Spirit-filled Christian, read any of the Apocrypha (catholic and orthodox Bibles have additional books), so whether they are also inspired by God is outside of my jurisdiction.