Mabinogion
It is composed of
- a classic tale of quest (much the same as Perceval), called Culhwch and Olwen
- Loud and Llefelys
- King Arthur, in a much different context than modern popular culture portrays
- The Four Branches of the Mabinogi with categories ranging from
- historic legend
- folklore
- mythology, etc.
Scholars of the 18th century to the 1970's have argued its authenticity as a whole. It has even been argued by some who have studied it, that the elven stories are fragmentary Celtic pre-Christian tales, and have thus been challenged as a collection at all.
However, since the 1970's, it's generally considered to have integrity. The plot structures, characterization, and language styles were analyzed. Thus, the conclusion that they are indeed a collection, with complex oral history overlaid with Anglo-French influences, arose. It was deemed a sophisticated narrative tradition.
Lady Charlotte Guest is credited with translation (in both English and Welsh), who allowed for subsequent translations to take place.