I finally finished The Life of Thomas More (Peter Ackroyd). As I mentioned previously, it was pretty painful (as evidenced by how long it took to finish).
The greatest error a student of history can make is that of anachronism - reading historical events into one's current context (ironically, this was common in medieval times).
So, when we think of the Popes, Kings, nations, and Church of More's time - we must not think of those things as they are now - but seek to set them in their own context.
For example, More's trouble (which led to his death) stemmed from the King of England (Henry VIII or H8) seeking a divorce (or annulment) from his wife. The Pope would not allow it, and the King declared the independence of the Church of England from the authority of Rome.
But the context is much deeper.
For example, there were four major super-powers in the West at this time: France, England, the Holy Roman Empire (effectively Germany), and the Vatican (which had its own armies for attacking neighbors) (there was also Spain, but it was unified with the HRE in 1516).
Furthermore, H8's wife (Catherine) was the sister of the mother of the Holy Roman Emperor (aunt of Charles V). But, the HRE and England often fought together with the Vatican against France.
Royal marriage was a diplomatic matter. Ann Boleyn was English, but had grown up in the royal court of France. Divorce was not just a theological or civil matter.
In the same vein, there were parallel secular and religious courts (heretics were tried in religious courts and then handed over to the secular authorities). Part of the issue was which court would have the highest authority - secular or religious.