Framing the story is the question of successorship of the throne of England, and it's neat to see how Follett weaves the characters' fictional lives into actual history as behind-the-scenes players.
I found it a very edifying and satisfying read, as you get to learn a lot about the period, and about construction of cathedrals. And it's an immersive read because the characters' motivations and knowledge are so deeply tied to the mindset of post-Norman England. It's interesting to think about what master builders of that period new and didn't know about engineering a cathedral.
Ken Follett writes simply; he does not dazzle with his use of language or artistry, and the plot is engaging but methodical, kind of like a protracted Elton John melody. He excels most due to his great characters.