So what is the significance of this building? Well, it's beautiful to begin with. Here are some pictures of the interior. Look at that marvelous ceiling. Also, notice how narrow the building is.
In the 13th century, the choir of the cathedral was rebuilt in the Gothic style, wider than the original and on a different axis. However, the new work was severely damaged by a fire in 1292, and the work was re-started. By 1322 the arcades and the easternmost bay were complete, with the elaborate tracery and glass of the east window being in place by about 1350. The upper stages of the walls were finished, probably by the architect John Lewen who died in about 1398. The Gothic arcade has richly moulded arches with dog's tooth decoration, and the twelve capitals are carved with vegetation along with small lively figures representing what is known as the labours of the months.
Here's another picture of that ceiling:
The book is what is known as an Alternative History. The prince had been given the name of Edmund at birth. So, what's the rest of the rest of Edmund's story? Well, you'll simply have to wait for the book!