Last July, as I have in 7 out of 10 of the last summers, I attended Cymdeithas Madog's one-week intensive Welsh Course, known to its friends as Cwrs Cymraeg. On Tuesday night we had "Pub Night", which included a quiz session, and one of the questions was "How many stories make up the Mabinogion?" As usual, I knew a little too much for my own good, so I asked in return, "Whose version?" The person asking the questions replied "My version!" which didn't help. If she had said, "Lady Charlotte Guest's version," I would have got the answer right, and it would have been "12". (No, not "42" - that's a different blog!) But I answered "11", and was adjudged wrong.
To explain my confusion, I should say that I collect versions of the Mabinogion. There are more than you might think, especially when you count scholarly editions of individual stories. The version most familiar to English-speakers, however, is the first English translation, published by Lady Charlotte Guest in the 1850's. It consisted of eleven stories from two 14th and 15th century Welsh manuscripts, plus the Tale of Taliesin from a much later source.
Let's start with the manuscripts. Of the two mentioned (the Red Book of Hergist and the White Book of Rhydderch), I have an edition of part of the latter, with additions from the Red Book -- Llyfr Gwyn Rhydderch: Y chwedlau a'r Rhamantau, edited by J. Gwenogvryn Evans and R. M. Jones and published by Gwasg Prifysgol Cymru in Caerdydd in 1973. Without going into details, this book contains the four related tales called Pedeir Kainc y Mabinogi (the Four Branches of the Mabinogi), the three Arthurian romances (Peredur, Gereint, and Owein), Breudwyt Maxen Wledic (M. W.'s Dream), Llud a Llevelis, Breudwyt Ronabwy (R.'s Dream), and the older Arthurian tale Kulhwch ac Olwen: a total of eleven stories.
Next in my library: Pedeir Keinc Y Mabinogi, allan o Lyfr Gwyn Rhydderch, by Sir Ifor Williams, published by Gwasg Prifysgol Cymru in 1951. This book contains only the Four Branches, and is more or less the standard edition. I also have separate copies of all the eleven stories with Welsh text and English commentary, mostly in the small red-bound editions published by The Dublin Institute For Advanced Studies in the 1980's. The exceptions are Patrick K. Ford's editions of Manawydan Uab Llyr (aka the Third Branch), Math Uab Mathonwy (the Fourth Branch), and Ystoria Taliesin, and Rachel Bromwich and D. Simon Evans' edition of Culhwch and Olwen. (I don't see Maxen Wledic on the shelf - maybe he's misfiled?)
Moving on to Modern Welsh editions and retellings, I have Y Mabinogion by Dafydd and Rhiannon Ifans (eleven stories), Gwerthfawrogi'r Chwedlau by Rhiannon Ifans (5 assorted tales with Welsh commentary), Y Mabinogi by Gwyn Thomas (an illustrated translation/adaptation of the Four Branches, aimed at children but equally delightful for adults), Culhwch ac Olwen (ditto), and several smaller excerpts and/or learner's versions of individual tales which I won't bother to catalogue.
On, then, to the English translations! The Mabinogion, translated by Gwyn Jones and Thomas Jones, is the most literal rendition and my favorite (I have two editions). This has the eleven tales from the Red and White books. My next favorite, Patrick K. Ford's The Mabinogi and Other Medieval Welsh Tales, has seven stories: the familiar Four Branches, Lludd and Lleuelys, Culhwch and Olwen, and his translation of the Tale of Taliesin (the first new English translation since Lady Charlotte Guest's, and from an earlier manuscript than the one she used). Then there is Jeffrey Gantz's The Mabinogion (eleven stories), and finally a new edition which I just acquired and recommend highly, Sioned Davies' The Mabinogion (eleven stories).
See why I was confused? In the last 150 years, so far as I know, Lady Charlotte Guest's book (and, I suppose, reprints derived from it) has been the only version of The Mabinogion to contain 12 stories. (But judging from my trawl through Amazon, my collection is by no means comprehensive!)
Why did she call it The Mabinogion, when most of my other versions use Y Mabinogi? Ah, that is a post for another day.