It is indeed an excellent example of ancient Gaelic literature. The book is mostly in verse attributed to St Caillin. It is written in the Spirit of Medieval Lives of the Saints, and extols the Saint, his Church and his famous relic the Bell of Fenagh. It is in fact a “Leabhar Sochair” (A book of advantage or profit) in which are recorded the claims of the monastery to rents and payments over a wide area. Stories are freely mixed with historical fact to achieve its purpose. It is mostly of interest, therefore from place names and a genealogical point of view. The Book was in the hands of the O’Roddys Coarbs of St Caillin until the early years of the 19th century when it passed on to the last member of the family Brian O’Roddy, Parish Priest of Kilronan. At his death it passed on to the then Bishop of Ardagh, Dr. Conroy. It was bought in 1888 from Rev. Denis Murphy S.J. by the Royal Irish Academy for ten Guineas. It was published in 1875 and again in 1939.
Divisions of Book of Fenagh
Part 1A Prose – Introduction and Genealogy of St. Caillin
1B 14 Poems Regarding Caillin, Magh Rein and Clog Na Riogh.
1C Prose Introductions to Poems.
2A Prose of St. Caillin and Tadhg O’Rodaigh
2B Statements by M O’Maolchonaire regarding Old Book of Caillin
3 7 Poems Regarding O’Donnell’s and others Families.
4 Genealogies of Conmaicne, O’Crachan and the Abbot of Fenagh
5 Poems Regarding Clann Neill and other Families and 1 Poem on St. Caillin
http://www.ria.ie/Library/Special-Collections/Manuscripts/Book-of-Fenagh