The main character is Thomas Cromwell, who rose from humble beginnings to become the King's most powerful advisor. The book tells a well-known story from a new angle. Mantel is more interested in character than in plot, which is good for me but fans of historical fiction might find it a bit too slow moving.
For the most part, Mantel's writing is beautiful without drawing attention to itself. However,there is one pervasive problem with the prose: it is often difficult to determine who the word "he" is referring to. It's a problem Mantel must be aware of, because she sometimes resorts to saying "He, Cromwell, ..."
I've now read three books by Hilary Mantel, all enjoyable and all very different: a contemporary thriller about expatriates in the Middle East (Eight Months on Ghazzah Street), a satire about a fat psychic whose spirit guide is an obnoxious drunkard (Beyond Black), and this historical character study. I don't know what to expect when I read a Mantel book, except that I will like it.