Originally written in Wales in Middle Welsh, but widely available in translations, the Mabinogi is generally agreed to be a single work in four parts, or "branches."
Early modern scholarship of the Mabinogi saw the tales as a garbled Welsh mythology which prompted attempts to salvage or reconstruct them.
Since the 1970s the tales have become recognised as a complex secular literature, though rooted in and containing elements of Welsh Mythology, with powerfully explored characters, political, ethical and gendered themes, as well as imaginative fantasies.
The style of writing is admired for its deceptive simplicity and controlled wordpower, as well as intricate doublets where mirrorings have been compared to Celtic knotwork.
It presents a legendary Britain as a united land under a king, yet with powerful separate princedoms, where native Welsh law, hud (magic), and romance, combine in a unique synergy.
Rhiannon then guides Pwyll through a cunning strategy using her magic bag which can never be filled, to extricate her from her betrothal to the princely Gwawl.
Gwawl is trapped in the bag and beaten by Pwyll's men until he agrees to Rhiannon's terms, including foregoing vengeance.
Rhiannon negotiates a penalty where she must sit at the castle gate every day for seven years telling her terrible tale to strangers and offer them a ride on her back.
Brân's half-brother Efnysien, angered that no one consulted him, insults Matholwch by mutilating all his valuable horses so horribly they become useless.
Brân the Blessed gives Matholwch compensation in the form of new horses and treasure, then added a magical cauldron (Welsh: Pair Dadeni) which can restore the dead to life, although the revived persons will always remain unable to speak.
Matholwch allows them to sway him, and casts Branwen away to serf in the kitchens, struck on the face every day by a low-caste butcher.
Brân, mortally wounded by a poisoned spear, bids the survivors to cut off his head, and take it to bury at the White Tower in London.
He prophesies his head will be their good companion and advise them, while they will sojourn for many years of idyllic feasting, first at Harlech in Gwynedd, then on the isle of Gwales in Dyfed.
Pryderi of Dyfed returns from the Irish War as one of its few survivors, to reunite with his mother Rhiannon, and his wife Cigfa.
The four of them, Pryderi, Cigfa, Rhiannon and her new husband Manawydan, become very good friends indeed, and travel the land of Dyfed admiring how bountiful it is.
In three towns in turn they craft saddles, shields and shoes of such quality that the local craftsmen cannot compete, so their envy becomes dangerous.
Once more living as hunters Pryderi and Manawydan follow a shining white boar to a strange castle.
After another attempt in England as shoemakers, the pair return to Dyfed, and Manawydan farms three fields of wheat next to Gorsedd Arberth.
Gwynedd in North Wales is ruled by the magician king Math fab Mathonwy, whose feet must be held by a virgin at all times except while he is at war.
He punishes the two brothers by shapeshifting them into animal pairs who must mate and bear young; first deer, then boars, then wolves.
Gwydion tricks her into naming the boy Lleu Llaw Gyffes (Bright Skillful Hand) by speaking to him, not knowing who he is as he is shapeshifted.
Gronw tells her to find out the secret of Lleu's protected life, which she does in the trust of her marriage bed.
The method is complicated, taking a year of almost impossible effort but Gronw completes it and Lleu falls to his spear, transforms into an eagle and departs.
Gwydion pursues a quest to find Lleu, who far away in eagle form perches up a tree, dying.
Gwydion tracks a sow which he finds eating maggots falling from Lleu's rotting body.
Gwydion sings a magical englyn (poem) gradually bringing Lleu back to humanity.
For the Welsh text in modernised spelling see J. M. Edwards, Mabinogion (o Lyfr Coch Hergest): Pwyll, Pendefig Dyfed, Branwen Ferch Llyr, Manawyddan fab Llyr, Math fab Mathonwy (Wrecsam: Hughes A'i Fab, 1921) The Four Branches are edited individually in Middle Welsh with English glossary and notes as follows: The three mediaeval manuscripts which have survived into modern times, were scribed in the 13th and 14th centuries, later than the compilation period of the work in the 11th century.
The Hopcyn library changed hands due to war and politics several times, with owners including the Vaughans of Hergest.
Later Tegid, as a senior bard and scholar, assisted Lady Charlotte Guest in her bilingual publication series, The Mabinogion, which brought the tales to the modern world.
Welsh Icons United a 2014 exhibition at the National Library of Wales, guested the Llyfr Coch, the Red Book, as part of its display; thus bringing the two main Mabinogi MSS.