To be frank, there are no original manuscripts remaining, and there is no firm evidence that it was produced at Clonmacnoise; however, it does focus on the parts of the country around Clonmacnoise—which was a center of learning and production of texts in Irish—and the clans that inhabited them. The Annals contain historical data on O'Kellys, O'Rourkes, O'Molloys, O'Connors, and McDermotts that we would not otherwise have.
The Irish Gaelic of the original was translated into English in 1627 by Conall MacGeoghegan, a descendant of Niall of the Nine Hostages.
This original manuscript, as well as the source from which it came, are both lost, but later edition copies of the translation exist in British and Irish museums. The translator noted that there were sections missing from the manuscript he had found (notably the years 1182-1199 and 1290-1299).
It begins "Adam in the 130 years of his age Begatt Seth, and afterwards Adam Liued 800 yeares & in all he lived 930 yeares." The first page quickly gets to Ireland:
This year of Lamech's age came the woman called Cesarea or Keassar accompanied onely with three men and 50 Women to this land which was the first habitacion of Ireland, though others say that this land was first Discouered and found by three fisher men who were sayleing in these parts of the world, and Because they made noe Residence in the land I will make noe mention of them.
There is scholarly demand for a modern edition to make the information contained available to more researchers.
I'm going to pick one brief entry for further talk. The sole entry for 670 reads "The Moone was turned into a sanguine collor this year." This was likely just a lunar eclipse. Did I say "just"? Lunar eclipses were of special interest to Christians and pagans. Let's talk about them tomorrow.