The subject of this study is the manuscript AM 557 4to, sometimes known as Skálholtsbók. The manuscript contains 12 Icelandic sagas, independent þættir and chivalric sagas (riddarasögur), but it is probably best known for being one of the main manuscripts of Eiríks saga rauða. The manuscript, written in the first half of the fifteenth century, is unremarkable in appearance; many of its leaves are not of full size and were probably like this from the beginning.

The author discusses the original composition of the manuscript, and also the content of the leaves now missing. A detailed investigation is made of the letter forms and their usage, and also of the orthography. Graphemic analysis is used in characterizing and grouping all the letters and signs in the manuscript; analysis of this data reveals that two scribes were responsible for producing AM 557 4to. The manuscript was previously dated to 1420–50, but the present study suggests that it may be somewhat older. The author compares AM 557 4to with the charter AM dipl. isl. fasc. VII 29, written on January 14, 1420, by one of the AM 557 4to scribes; the investigation suggests that the manuscript was produced before the charter.

The present study is an important contribution to the field of manuscript studies. The investigation adds to our knowledge of fifteenth-century Icelandic manuscripts and also shows the importance of graphemics in examining medieval script, orthography and scribal hands.