I'll use my final vote to nominate
The Iron King by Maurice Druon. George RR Martin called it "the original Game of Thrones", which is why I had it on my wish list.
Goodreads blurb:
The Iron King – Philip the Fair – is as cold and silent, as handsome and unblinking as a statue. He governs his realm with an iron hand, but he cannot rule his own family: his sons are weak and their wives adulterous; while his red-blooded daughter Isabella is unhappily married to an English king who prefers the company of men.
A web of scandal, murder and intrigue is weaving itself around the Iron King; but his downfall will come from an unexpected quarter. Bent on the persecution of the rich and powerful Knights Templar, Philip sentences Grand Master Jacques de Molay to be burned at the stake, thus drawing down upon himself a curse that will destroy his entire dynasty
Originally published in 1955 in French.
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Also available on Overdrive