The Bible, as a source of spiritual truth, I find to be pretty much useless, outside of the gospels, which I don't find to be containing the fullness of said truth.
How truth is discerned is a personal matter. I go with my intuition and my heart. Others go with the Bible itself, but I see no reason for it personally. Still others go with a churchly authority, which I've tried time and again and I just can't fit in that box.
Most define Christianity in some way in relation to the Bible. Me, I'll take the four Gospels, but I won't take them 100% literally, because I don't believe Jesus tossed demons into pigs (for example). I'll also consider the non-canonical gospels. And Tarot cards. And the Qu'ran. And the Tao te Ching. And and and ...
The church is the candle before me, the books beside me, the heart within me, and you, and me.