The Faddan More Psalter is composed of 60 sheets of vellum which are divided into five gatherings, or quires.
The text is based on the Gallican Psalter, a version of the Latin Psalter devised by St. Jerome in the late 4th century. The text is written with iron gall ink, and a red and yellow pigments are used for decoration. It contains the standard 150 psalms. The opening letter of each psalm is marked by a capital and the opening words of Psalms 1, 51, and 101 are decorated, a convention used in other Irish psalters. The text of the Psalter is arranged in a single column. The script is in the style termed Insular majuscule. It probably developed in Ireland but was used in the common cultural area of Ireland and parts of Britain.
The Faddan More Psalter survived because it was in a wet environment, not exposed to air. Preservation of the book varies greatly from page to page. In some cases only the edges survive, and loose letters are all that remain of the centre of the pages. In other cases, almost full bifolia have been preserved.
Because of its deteriorated state, the manuscript could not be preserved as found. Conservation involved excavation of the book block in the laboratory, each sheet being separated and cleaned individually. The water content in each separated fragment was replaced with a solvent, dried, and preserved under vacuum to prevent shrinkage.
Most surviving medieval manuscripts are not contained within their original cover. The cover of the Faddan More Psalter is therefore an extremely valuable resource for the study of early book making. The cover is a wallet-shaped piece of folded leather.
Three horn buttons affixed to the flap may have been used to secure straps that wrapped around the cover. The manuscript was not attached to the cover, but the gatherings were bound together with vegetable fibre. The outside is dyed with a black carbon-based pigment.
The cover of the Faddan More Psalter was also used by scribes to try out designs, possibly before they decorated other manuscripts, and faint patterns of interlace are visible on the outside of the cover. The inside of the cover is lined with papyrus, a writing material produced from reeds grown in the eastern Mediterranean, famously in Egypt. The papyrus was probably placed inside the cover to act as a stiffener. The presence of papyrus emphasises the far-reaching contacts of the early Irish church.
Similar covers are seen in depictions of books in contemporary manuscripts and indicate that this was a popular type of cover. The early medieval Gospels of Cadmug and MacDurnan and the Book of Dimma depict comparable covers.