The most valuable manuscript collections of early Welsh poetry are preserved in what their first editor termed the 'Four Ancient Books of Wales'.
These bear titles redolent of ancient mystery:
'The Black Book of Carmarthen',
'The Book of Taliesin',
'The Book of Aneirin',
'The Red Book of Hergest.
'The Black Book of Carmarthen' and 'The Book of Aneirin' were probably compiled some time around the year 1250;
'The Book of Taliesin' a little later, perhaps 1275;
whilst The 'Red Book of Hergest' was 'written with few exceptions during the last quarter of the XIVth and the first quarter of the XVth centuries.'
The Red Book contains a great deal of prose literature,
including the famous tales known as Mabinogi and a Welsh version of Geoffrey's History
(The Historia Regum Britanniae of Geoffrey of Monmouth.
Otherwise the contents of all four books comprise a wonderful collection of Welsh verse,
much of it far older in origin than the manuscript in which it has chanced to be preserved.
The above text is from:
"The Quest for Merlin"
by Nikolai Tolstoy
publisher: Sceptre 1985