The only reason I finished this book was that the time period facinates me and I was curious to see if I could figure out why everything in Follett's novel was so uninspiring. Here are the major problems:
1. Follett has obviously done his research on the period, other than the language, but he lets it take center stage, to the detriment of his characters. It feels like he created a list of stock items from the middle ages and checked them off as he went along -- horny bishop: check; power-hungry priest: check; lesbian nun: check; lord of the manor who thinks his serfs don't matter as humans: check; black death: check; etc., etc., etc. He even brings in the flagellants, for no apparent reason, even though they really didn't exist to any significant degree in England. Most of it doesn't advance or have anything to do with the story -- it's just there so that he can get in everything having to do with the 14th century.
2. The characters don't feel like real people. It is possible to set a book in this time period and put characters in it that seem to live and breathe and make you care about them. Connie Willis' The Doomsday Book does this really well. When her characters die, you cry. Follett's main characters all miraculously survive the horrors of the century, and it's only the peripheral characters who die. Yet you don't feel their pain or their triumphs or anything much. They just don't seem real.
3. Follett attributes a 21st century sensibility to the characters that is out of keeping for even the most progressive people in the 14th century. I love the idea of a woman who wants to break out of the servitude and inferiority of women in the middle ages, but Caris, the lead female character, is an outright feminist. And when Merthin, the main male character, discovers that one of the monks in the town has been stealing things, he wonders if maybe it's a sickness. Give me a break! The notion that something that was considered a sin might have been caused by mental illness just didn't exist in the 14th century. The book is riddled with anachronistic attitudes such as these.
4. As other reviewers have pointed out, the book is filled with words and phrases that didn't exist in the 14th century. I appreciate that Follet has tried to make the language sound natural, rather than using the syntax of the period, which would have sounded natural to people in the middle ages but wouldn't to us. But using words like "senility" (which the Oxford English Dictionary records as not having appeared in pring until 1791), phrases like "gone missing" (a 20th century creation), etc., doesn't sound natural, it just takes you even further out of the time period. Particularly noticeable is that the characters call the plague "the plague." "Plague" wasn't used for any illness until much later. The people who lived through the Black Death (another term from much later) called it the "pestilence" or the "Great Mortality." They definitely did not use the term plague. If you don't know this, it might not make much difference to your enjoyment of the book, but if you're a history buff, things like this just take you further out of the action. Given how much research Follett obviously did on the period, the inattention to language just seems sloppy.
5. Some people have been offended by the amount of sex in the book. It's not the amount that's a problem. Let's face it -- there was no t.v., few people had books, and the main form of entertainment you could have after dark was sex. So it's not surprising to find alot of it. The problem is that it's gratuitous and written from a real male fantasy perspective. A sample from one of Follet's less graphic passages: "Caris had never seen Mair undressed, and she could not resist a peek. Her companion's naked body took her breath away. Mair's skin seemed to glow like a pink pearl. Her breasts were generous, with pale girlish nipples, and she had a luxuriant bush of fair public hair." And seriously -- how many times does Merthin have to look at a pillar and remember the time he "felt up" Caris there?
6. The mystery at the core of the book, having to do with the death of Edward II, is lame and implausible and there's really not much of a payoff. It feels tacked on in order to give the sense of a story, when the book is really not much more than a survey of the middle ages (albeit with the tacked on attitudes of modern times for the main characters).
I was so excited about reading this book, but it was a major disappointment, neither moving, nor particularly entertaining or informative. If you want to learn about the 14th century, I'd recommend Barbara Tuchman's "A Distant Mirror: The Calamitous Fourteenth Century", Thomas Costain's series on the Plantagenets, particularly "The Three Edwards" (which covers the 14th century), Jonathan Sumption's books on the Hundred Years War, Paul B. Newman's "Daily Life in the Middle Ages," or for fiction, the aforementioned "The Doomsday Book." All would be better choices than this long (over 900 pages) and unengaging volume.