Geoffrey of Monmouth 
The History of the Kings of Britain [EPUB ebook] 

First appeared in the 1130s and originally composed in Latin as
‘Historia regum Britanniae’, ‘The History of the Kings of Britain’ by Geoffrey of Monmouth claims to be a history of Britain’s kings from the island’s founding by Trojan descendent Brutus in 1200 BCE, to the Britons’ abandonment of the island in the seventh century CE.
‘The History of the Kings of Britain’ was immediately popular, inspiring retellings and adaptations by writers and artists through the centuries. Because its historical merit is almost non-existent, it has been called an epic in prose and treated as a literary text whose primary purpose is patriotic. It is credited with introducing the figure of Merlin and elevating King Arthur to mythic status.