Ghost on the throne by James Romm( non fiction)
I have found myself somewhat obsessed by Alexander the Great and having read several books of his campaigns, was left wondering what happened after he died. The answer is that the Diadochi had a series of never ending wars with shifting allegiances over decades. I was particularly taken with his elite troop, the silver shields who were middle aged men when he inherited them from his father and where still utterly unbeaten and unbeatable decades later in their seventies, still beating every enemy they met. They reminded me of a group of Cohen the barbarians from discworld.
The White ship by Charles Spencer.
Another non fiction about the sinking of the white ship in 1120 with the sole heir to the throne on board and how that one event was probably the single most colossal upheaval in British history. A true life game of thrones.