Was this before or after GoT? Seems to be when Targaryen's were in their prime, had bigger dragons, were a force to be reckoned with until some civil war and then they destroyed themselves.
shareFrom memory it's a couple of hundred years before the events in Game of Thrones. All I know is that it seems people were not as interesting back in those days, or as good looking.
Before, I believe they're starting when Aegon the Conqueror came out of the ruins of Valyria with an army of dragon-riders, and conquered Westeros kingdom by kingdom.
It's territory covered in the book "Fire and Blood", by GRRM, and the book is written in a very dry pseudo-historical style. It does NOT record what the people of Westeros thought about being conquered by foreigners who rode fire-breathing monsters and married their sisters, but that's something the show will have to go into. I wonder if Aegon and his sister-wives will be played as villains, or just more players in the game of thrones?