A short summary: Mary Stewart was the only child of James V of Scotland. For political reasons, she was betrothed to Francis, the sickly heir to the French throne. She was taken to France when she was four and lived there until she was 21. She was raised a Catholic. She and Francis were married when they reach appropriate age, but he died shortly thereafter.
James V died when Mary was very young and Scotland had been ruled by a regent. Mary now returned home to take over her rightful throne. After a few years, she married Lord Darnley, who was only 20. It was with Darnley that Mary gave birth to a son, the future James VI of Scotland and James I of England. Darnley was a pompous, conceited lad, and the power went to his head. He quickly annoyed the Lords of Scotland and they conspired to get rid of him.
While recovering from sickness in Edinburgh, the house he was in exploded. When Darnley’s body was found, however, he had been suffocated.
The murder threw the kingdom into turmoil. One of Mary’s advisors, the Earl of Bothwell was implicated in the murder. Things were really roiled up a bit later when Bothwell kidnapped Mary, raped her (probably) and then married her. A group of Protestant Lords rebelled. Mary fled to England, hoping for help from Queen Elizabeth. (Bothwell fled to Norway where he was captured and kept as a political pawn until he died, insane, in prison.)
Elizabeth was a shrewd woman who did exactly what was best for Elizabeth. In Mary’s case, Elizabeth couldn’t decide what her best interests were, so she did nothing, keeping Mary a prisoner of sorts for the next 19 years.
The major issue was that Mary was next in line for the English throne. Elizabeth was worried that Mary’s followers would murder her and put Mary in her place. There was also the additional concern that Mary was Catholic. When interest in Mary had died down sufficiently, Elizabeth’s men concocted a plot to frame Mary for treason (a legal impossibility since Mary was the ruler of another nation). She was tried and beheaded.
When Elizabeth died, Mary’s son became king of the combined kingdoms of Scotland and England.

Book review: For the most part it was interesting. It bogged down some toward the end because being shut up in a castle for 19 years doesn’t make for very exciting stories. Fraser could have done a better job of introducing the major players around Mary. She kept mentioning them before they took part in affairs and never really explained who exactly they were or why they mattered. This wasn’t helped much by the fast that half of them were named Stewart or Stuart and that they changed names every time they got a new title.
Fraser was definitely a fan of Mary’s. She worked hard to prove that Mary was beautiful, all contemporary paintings to the contrary. It does seem that most men who got to know Mary well fell in love with her to some extent, and all contemporary descriptions make note of her beauty and grace. She must have been a delightful girl, but I saw nothing in this book that indicated that she was fit to rule a country.