The bible does not contradict itself. The people who read and interpret it does!
Or....Some people who read and interpret it adopt harmonizing interpretations that overlook contradictions that arise when 66 originally independent books are brought together into an anthology and treated as a single volume. These harmonizations are automatically preferred no matter the actual merits of the interpretation, even if it is less likely to represent the view of the author than the non-harmonizing perspective. Usually, if a harmonization is merely possible, this is taken as ipso facto proof that the contradiction does not exist.
It is certainly true that some contradictions do not lie in the text and result from the way the text is interpreted. But most, if not all of them? I believe most instead are simply due to the ecclectic nature of the text itself.