Editor of the major anthology 'The Mabinogi: a book of essays' (NY: Garland Publications, 1996)
Republished (NY: Routledge 2015).

The 1970s - 90s was a pivotal period in Mabinogi Studies, a paradigm shift, and Sullivan's anthology neatly captures the shift in its collected essays from the period. The 2015 reprint sold out within only two years, demonstrating how important it is to any serious student of the Mabinogi. (Some of its content is available on googlebooks, and of course via libraries.)
Sullivan explains ”I published the book because I was tired of having to sort through pages of articles I had copied from various journals.” So he put them in a book. His Introduction is genuinely helpful as an overview of Mabinogi Studies up to 1996.
Sullivan’s own particular field is modern interpretations on which he is insightful and incisive. Here is an accessible example of his thinking. <http://www.celtic-cultural-studies.com/papers/04/sullivan-02.html>
The student needs to be aware that much of the book is packed reading, which cannot be absorbed in one read through. But patiently re-reading each article, will repay the effort. See notes below the Contents list for help.

Sullivan, Charles William, ‘Preface’, pp. xi-xiii.
Sullivan, Charles William, ‘Introduction’, pp. xv-xxi.

# ORIGINS
Bromwich, Rachel, ‘The Mabinogion and Lady Charlotte Guest’, pp. 3 – 18.
Charles-Edwards, T.M., ‘The Date of the Four Branches of the Mabinogi’, pp. 19 -58.
# COMPARATIVE ANALYSES
Wood, Juliette, ‘The Calumniated Wife in Medieval Welsh Literature’, pp. 61 -78.
Keefer, Sarah Larratt, ‘The Lost Tale of Dylan in the Fourth Branch of the Mabinogi’, pp. 79 -98.
Ford, Patrick K., ‘Branwen: a study of the Celtic affinities’, pp. 99 -120.
Welsh, Andrew, ‘Manawydan fab Llyr: Wales, England, and the “New Man’, pp. 121-141.
# STRUCTURE
O'Coiledin, Sean, ‘A Thematic Study of the Tale Pwyll Pendeuic Dyuet’, pp. 145 -151.
Hanson-Smith, Elizabeth, ‘Pwyll Prince of Dyfed': the narrative structure’, pp. 153-164.
Bollard, John K., ‘The Structure of the Four Branches of the Mabinogi’, pp. 165 -196.
Ford, Patrick K., ‘Prolegomena to a Reading of the Mabinogi: Pwyll and Manawydan’, pp. 197 -216.
Jones, R.M., ‘Narrative Structure in Medieval Welsh Prose Tales’, pp. 217 -262.
# THEMATIC
Gantz, jeffrey, ‘Thematic Structure of the Four Branches of the Mabinogi’, pp. 265-275.
Bollard, John K., ‘The Role of Myth and Tradition in the Four Branches of the Mabinogi’, pp. 277 -302.
McKenna, Catherine, ‘The Theme of Sovereignty in Pwyll, pp. 303 -330.
Valente, Roberta, ‘Gwydion and Aranrhod: Crossing the Borders of Gender’, pp. 331 -345.
Sullivan, Charles William, ‘Inheritance and Lordship in the Math’, pp. 347-366.

Works Cited, pp. 367-382.
About the Contributors, pp. 383-387.

This is not an exhaustive list but gives an idea of Sullivan's work apart from the Anthology.

Sullivan, Charles William III, ed., Welsh Celtic Myth in Modern Fantasy (Greenwood Press, 1989).
Sullivan, Charles William III, ‘Inheritance and Lordship in the Math’, Cymm. (1990) pp. 45–63.
Sullivan, Charles William III., ‘Folklore and Fantastic Literature’, Western Folklore, 60 (2001) pp. 279–97.
Sullivan, Charles William III, ‘Conscientious Use: Welsh Celtic Myth and Legend in Fantastic Fiction’, Celtic Cultural Studies, (2004) <http://www.celtic-cultural-studies.com/papers/04/sullivan-02.html>
MANY MORE <http://www.isfdb.org/cgi-bin/ea.cgi?21246>

Charles William Sulliva III, b. 7 June 1944, Kingsport, Tennessee, USA.
Professor of English at East Carolina University: American Folklore and Northern European Mythology.

The collection of articles covers research from Bollard’s pioneering 'Thematic Structure' (1974) onward, which radically changed the way the Mabinogi is approached from ‘mythic remains’ to ‘sophisticated literature.’
The reader should be aware this is a studious book, and not a retelling of the tales. One or more of the Mabinogi texts is necessary independently. (Recommended Ford, Bollard, or Davies, or see Will Parker free online.) If willing to read each article more than once, this is a rich treasure house. If willing to make notes, and return again and again, the rewards never stop for there is so much here. I am still learning from it after 12 years acquaintance, and my third copy.
Charles Sullivan said he just got tired of fetching different articles from different journals so he collected the most important ones together. In the mid 1990s computers and the net were just becoming widespread, so it is much easier now to get PDF copies of articles. It still means separate searches, registering into separate systems, and older PDF files are cranky to handle. Having so many of the key texts from this crucial 20 year period gathered together, is a godsend for efficient research, easier learning, and thoughtful comparison.

The Introduction by Sullivan gives an overview up to the date of publication (1996) which stands the test of time very well.
The first section lays down the historical background. Bromwich on the formidable 19thC Charlotte Guest is dated in places but still a good summary. It has one of the best accounts around on William Pughe, the real pioneer of modern Mabinogi publications. (Bromwich takes most of her information from Phillips (1921). For the best recent summary of Guest see Sioned Davies, 2004.)
Charles-Edwards on dating is a classic, detailed and venerable, but in places, dated; reference should be made to Rodway (2012) pp. 5-13. Charles-Edwards' level of detail is really only for the advanced student.
Folklore, tale types and motifs held a strong place through the 20thC. Wood’s 'Calumniated Wife' analysis is a standard classic, although in my view, the application of the motif fails as Rhiannon and Branwen deviate from the pattern in too many ways (as Wood herself mkes clear). Nonetheless this kind of analysis was a standard part of the field in the second half of the 20thC, so needs to be included. Keefer’s contribution looks at selkie legends to expand the Dylan fragments.
Almost all the rest of the articles demonstrate just how powerful the new structural analysis was (and is) which Bollard (1974) pioneered. The development is well represented additionally by Gantz, Ford, Welsh, O’Coileain, Hanson-Smith, and R.M.Jones. I would especially recommend Jones' article to explain the structural approach. The structural method looks at how events in the tales form patterns, not just in timed sequence as a 'natural' telling, but in multiple connections of resemblane, rather like clicking links on a website for a similar example. Parallels can be traced like this which enrich our understanding. An example is the similar forms which Pwyll’s two relationships with Arawn and Rhiannon take.
The contemporary audience would have been used to recognising these parallels as a sophisticated game. The ‘messages’ of this example are first, that Rhiannon is implicitly of the Otherworld of Annwfn, like Arawn, though this is not anywhere actually stated. The bracketing of a woman with a crowned king of the powerful land of Annwfn, demonstrates how eminent she is, and how powerful a woman in this world could be. Bollard suggests the overall themes of these ‘interlaced’ patterns are ‘marriage, friendship, and feud.’ Gantz also suggests a broadly moral message. (Miles-Watson (2009) is a powerful recent application of the technique.)
Sullivan divides these structural essays into Thematic and Structural sections, but as he notes in his useful and succinct Introduction, the split overlaps, so is only an approximation.

The full range of essays also fill out deeper understanding of the tales background in mediaeval politics: Irish influences (Ford), sovereignty (Mckenna), lordship (Sullivan), gender (Valente, Welsh).
Space precluded some items. An excerpt from Jackson's International Tale (1961) on motif analysis would have been apt, however the approach is represented by Wood's 'Calumniated Wife'. A snippet of WJG as background, perhaps from his 1958 Folklore and Myth, would have been good balance, as he was so influential with his fanfic mythology constructions. Mac Cana is apparently missing but appears in several articles quoting him. Sullivan remarked to me that he would also have liked to include Sims-Williams.
The most important omission in my view, is Sioned Davies with her storytelling approach. Her 1992 'Storytelling in Medieval Wales' would have been perfect (readers can access it via the Oral Tradition journal online). The lack of a page Index is the major weakness of this precious resource, but Sullivan has confirmed this was very much about space restrictions.
Given carefull re-reading, one at a time, the articles in this anthology provides an almost complete portrait of how Mabinogi Studies changed its paradigm. Mythological analysis is still fascinating, but it inevitably presents a narrative of sadly broken 'remains'. The new perspective of a coherent, intricate literature, provides a vigorous, intact work of genius to rival the best literature in Europe.
These were after all, the first prose tales we know of to be placed on record. Sullivan's project is a major aid to support the Mabinogi's claim to classic genius.

This Notes section is an updated version of a book review submitted to Amazon (2/08/2016).