The Iron King by Maurice Druon

Philip the Fair, King of France, is a man born to rule. His iron hand has built France into a powerful and peaceful nation. To further strengthen France, the errant Knights Templar have been hunted down. Now as their leaders are executed, a curse is uttered. So begins the Accursed Kings series. Phillip's sons are weak and cuckolded, while his iron hearted daughter is married to a weakling king of England who loves his male courtiers. Curses, manipulations and lies surround the throne.
I loved this book. I received The Strangled Queen from the publisher and knew I needed to start at the beginning. This series is amazing. Read it!