Maurice Druon, The Accursed Kings historical novels -- read them all as a teenager. For a while they made me an expert in medieval French history. I remember little by now, but I did remember the story of Jacques de Molay and was under the impression, for many years, that the curse concerned not just the Capetian dynasty but all of Europe. I don't remember why I interpreted it this way, but there you have it.
The dynasty that went a long time before that one, the Merovingians, I find particularly interesting. In their heyday they established the largest kingdom in Western Europe after the fall of the Roman empire (if there really was such a thing as "the fall" -- to me it seems more like the refurbishing/recalibration). What I find special about them is that to this day, chronicles exist that officially derive their genealogy from a sea monster, a “quinotaur,” who had a relationship with the ancestress and produced Meroveh, the founder of the dynasty. This gave the dynasty sacral pre-Christian legitimacy—a ruler whose authority comes from the sea/chaos/the Other. (Just like Chinese emperors who derive their Mandate to rule from the dragon. Chinese dragons spend the first one thousand years as water creatures, then develop flight and take to the sky, the mountains, and the imperial court, as the case may be.)