I find the idea of who these people were and what actually happened back then with the origins of Christianity, against how the RC church manipulated stuff and changed everything, absolutely fascinating.
Now I'm not Catholic, but I do groan when people say this. The Roman Catholic Church has never been anything like in full control of what Christians believed. Christianity itself has never been unified.
In the early years, there were Orthodox and Arian Christians who flat disagreed with each other. When what we now know as standard Christianity prevailed, the church was still organised very much on the local level, with the bishops being the only people who had much clout, and then only in their own areas.
In early mediaeval times, large parts of Europe, although Christian, had very very little to do with the Pope. A good example is the Celtic church in Scotland, Ireland and northern England: they considered themselves part of the church, but simply looked after themselves. While the popes did increase their powers over time, in 1054 the church split in two (Catholics and Orthodox) and any control the popes had over the east vanished. Even after then, the churches in places like France and England had their own distinctive practices and beliefs, as did local areas. After the Reformation, the Pope lost control of northern Europe too.
Finally in terms of doctrine, there was far more philosophical debate than people realise. It wasn't exactly like The Name of the Rose. At the local level, people mixed all sorts of local beliefs in with their Christianity. Many of these beliefs survived well into modern times.