[1] The book contains some of the oldest surviving specimens of Old Irish and for being one of the earliest manuscripts produced by an insular church to contain a near complete copy of the New Testament.

Research has determined, however, that the earliest part of the manuscript was the work of a scribe named Ferdomnach of Armagh (died 845 or 846).

Ferdomnach wrote the first part of the book in 807 or 808, for Patrick's heir (comarba) Torbach, abbot of Armagh.

It remained in the hands of the MacMoyre family in the townland of Ballymoyer near Whitecross, County Armagh until the late 17th century.

In 1853, Reeves sold the Book to John George de la Poer Beresford, Archbishop of Armagh, who presented it to Trinity College, Dublin,[4] where it can be read online from the Digital Collections portal of the Trinity College library.

Folio 32v shows the four Evangelists' symbols in compartments in ink, the eagle of John resembling that of the Book of Dimma.

Charles Graves, who deciphered in 1846 from partially erased colophons the name of the scribe Ferdomnach and the bishop Torbach who ordered the Book.

The manuscript also includes significant portions of the New Testament, based on the Vulgate, but with variations characteristic of insular texts.