Non-fiction but incredibly evocative of the ASOIAF milieu:
https://www.amazon.com/Plantagenets-Warrior-Kings-Queens-England/dp/0143124927
How about historical non-fiction?
https://www.amazon.com/Plantagenets-Warrior-Kings-Queens-England/dp/0143124927
https://www.amazon.com/gp/product/B00INIXM42/ref=dbs_a_def_rwt_bibl_vppi_i2
This is incredibly evocative of ASOIAF, or, more accurately, ASOIAF is incredibly evocative of these periods of English history.
https://www.amazon.com/Plantagenets-Warrior-Kings-Queens-England/dp/0143124927
Pretty good book about the Plantagenets who ruled England (and at times parts of Ireland, Scotland and Wales) during the time period you're talking about.