The volume contains some of the oldest poems in Welsh, possibly but not certainly dating back to the sixth century and to a real poet called Taliesin.

[5] Ifor Williams similarly describes the Canu Taliesin as credibly being the work of Taliesin, or at least 'to be contemporary with Cynan Garwyn, Urien, his son Owain, and Gwallawg', possibly historical kings who respectively ruled Powys; Rheged, which was centred in the region of the Solway Firth on the borders of present-day England and Scotland and stretched east to Catraeth (identified by most scholars as present-day Catterick in North Yorkshire) and west to Galloway; and Elmet.

Re-examining the linguistic evidence for their early date, Patrick Sims-Williams concluded in 2016 that evaluating the supposed proofs that poems in the Books of Aneirin and Taliesin cannot go back to the sixth century, we have found them either to be incorrect or to apply to only a very few lines or stanzas that may be explained as additions.

[8] Among probably less archaic but still early texts, the manuscript also preserves a few hymns, a small collection of elegies to famous men such as Cunedda and Dylan Eil Ton and also famous enigmatic poems such as The Battle of Trees, The Spoils of Annwfn (in which the poet claims to have sailed to another world with Arthur and his warriors), and the tenth-century prophetic poem Armes Prydein Vawr.

Many poems in the collection allude to Christian and Latin texts as well as native British tradition, and the book contains the earliest mention in any Western post-classical vernacular literature of the feats of Hercules and Alexander the Great.