La Reine Margot, by Alexandre Dumas
Charles cocked his arquebuse, and, stamping his foot with blind rage, cried as he dazzled Henry's eyes with the polished barrel of the brandished weapon, "Will you accept the mass?"
Henry remained mute.
Charles IX shook the vaults of the Louvre with the most terrible oath that ever issued from the lips of man, and grew more livid than before.
"Death, mass, or the Bastille!" he cried, taking aim at the King of Navarre.
This historical epic of the French Renaissance lends itself to the Game of thrones universe, with Catherine de Medici in the Cersei Lannister role, Charles IX as Robert Baratheon, and Margot as Sansa, with the distinction that many or most of the most bloody things in the novel actually happened.
The Red Wedding St. Bartholomew's Day massacre occurs early in the novel, and the body count only goes up from there. Assassinations, attempted assassinations poisonings, torture, hunting party 'accidents', duels and other treachery abound, as well as implied sorcery, prophecy, curses and other supernatural tactics and events. The first chapter is an information dump about an abundance of kings, dukes, Catholic and Huguenot partisans and their families, that must be studied closely so that you understand who hates who and why before proceeding to the ensuing carnival of carnage.
Two stories stand out in the middle of it all. One concerns the redshirts La Mole and Coconnas, who might as well be the Two Musketeers as they stand on the ground looking up and commenting at the intrigues and skullduggery of the high and mighty above them while providing a dose of Stark Family honor and friendship to a world where such things are derided as weakness. The second, and central, story, is about Henry, King of Navarre, and his arranged marriage to La Reine Margot, daughter of Charles IX. The two do not love each other, and each has a lover on the side, but they respect each other with enough platonic affection to join forces and get one another out of jams.