The Pillars of the Earth

This massive 983-page tome is well worth it. You might look at it and think it's intimidating and would take forever to read, but it is a very approachable page-turner. The Pillars of the Earth (1989), by Ken Follett, is set in medieval England and includes characters high and low through a couple of generations. The characters are well-developed, and the settings and times are vividly described.

from the publisher:

As a new age dawns in England's twelfth century, the building of a mighty Gothic cathedral sets the stage for a story of intrigue and power, revenge and betrayal. It is in this rich tapestry, where kings and queens are corrupt, that the common man shows eternal promise - and one majestic creation will bond them forever...

from wikipedia:

The book traces the development of Gothic architecture out of the preceding Romanesque architecture and the fortunes of the Kingsbridge priory against the backdrop of actual historical events of the time.

The author's site has information, including a reading and discussion guide. Oprah also has a guide.