Third in the series Codices Hibernenses Eximmii, the Book of Ui Mhaine is miscellaneous in content, comprising a wide range of texts in Old, Middle and Early Modern Irish, in prose and poetry, and covering a diverse range of genres from history to poetry, grammar to dindshenchas, glossaries to genealogies. Miscellaneous, however, should not necessarily be understood to mean random. Certain thematic clusters can be identified, and the layout and juxtaposition of texts appear to be both deliberate and meaningful. While the manuscript contains much that represents senchas, that is, the learned historical discourse of medieval Ireland, there is also much about the manuscript that is more innovative, not least 'the free mixture and association of contemporary poetry and older poetry in a single book'. Many of the poems in the manuscript are of particular social or political importance, and a significant number of them are uniquely preserved in the Book of Ui Mhaine.
