As a history major I learned dribs and drabs about the English monarchy but never really looked at the family tree, so to speak. There's a lot in ROYAL PANOPLY I wasn't aware of.
Carolly Erickson starts with William the Conqueror and works her way all the way down to Queen Elizabeth II. I don't know if it's Erickson's cynical tone or William the Conqueror's suspect genes but these monarchs suffer in the telling. Sadists, ne'er-do-wells, spendthrifts, and the mentally ill abound.
Many of them begin their reigns as forceful kings. Henry II brought order to a land "plundered and battered by oppression" but ultimately wound up being responsible for the murder of his former friend, Thomas Becket. Henry V (Prince Hal) conquered the French at Agincourt but his religious scrupulosity contributed to his death at only thirty-four. Even William the Conqueror died alone, his body robbed by his servants.
Erickson pulls no punches with modern sovereigns. Queen Victoria, after the birth of a son with hemophilia, turned on Prince Albert accusing him of hardheartedness, thus contributing to his early death. Erickson has even less regard for Queen Elizabeth II. We learn that it has been some time since she and Prince Phillip have slept in the same bed, due to Phillip's affair with another woman. According to Erickson, "the throne has become a symbol, not of moral force, but of moral vacuity."
Carolly Erickson's organizational approach leaves a bit to be desired as well. There is quite a bit of repetition as she begins each new biography, but just when you're looking for a recap, as in the case of the ascent of the Stuart kings, you don't get it. James I of Scotland took the throne because of Mary Queen of Scots's claim but we never do find out how she was related to the previous monarchs. One bit of misinformation that is cleared up, however, is that England was invaded more than once after William the Conqueror in 1066. King Edward IV, who had been temporarily deposed, invaded from the Low Countries, unseating ineffectual and insane Henry VI and having him put to death. Also, William of Orange invaded after James II tried to reinstate Catholicism. He was invited by several members of Parliament but not officially. James could have defended his crown but panicked and left the country without putting up a fight.
One thing we can definitely learn from reading PANOPLY is what a ludicrous system of government monarchy really is. The British were stuck with some of these people. All we need to do is look at George III-IV. George was thought to be insane (actually he had Porphyria) but his son was worse. He was a drunk and a womanizer who never bothered to be at all discreet. The man made Prince Charles look like Mother Theresa. And if you think he may have been an anomaly take a look at Edward VII, Victoria's successor. Bertie, as he was known in the family, was addicted to gambling, drink, and women; his ministers ignored him, never considering his opinions worth asking for. Yet he was king from 1901-1910. 

Dave Schwinghammer's published novel, SOLDIER'S GAP, is available on amazon.com.