What counts as New Testament?

episode 9 of The end of the Early Church (and the start of the Middle Ages)

There are 27 books in the New Testament.

Why not 24?

Why not 30?

How did these books come to be accounted inspired Scripture, and why?

Who got to decide which books count as 'sacred Scripture'?

And if it was the institutional Church that decided — doesn't that mean that the Church is a higher authority than the Bible?

We dive, fearlessly (because, stupid), into these thickets....