He reworked the poem over the course of the following decade, during which he also elaborated an erudite commentary in the form of marginal and interlinear glosses. Boccaccio’s autograph of the Teseida—a manuscript of the poem transcribed in the author’s hand—is currently housed in the Biblioteca Medicea Laurenziana in Florence. The autograph dates to a decade after the poem’s initial composition: its multi-layered construction reflects its re-elaboration and gradual accretion.

The Teseida consists of twelve books written in octaves of hendecasyllables, a strophic form that Boccaccio probably adopted from oral cantari (narrative poems performed in public) and whose rhyme scheme he regularized into the form’s definitive ABABABCC pattern. Boccaccio accompanied the poem with a rich paratextual apparatus, beginning with a dedicatory preface to the beloved Fiammetta and a sonnet introducing the work as a whole. Each book is also headed by a sonnet that summarizes its content. Two caudate sonnets close the work: an invocation to the Muses and the Muses’ response. Authorial rubrics divide the poem into narrative sub-units and a sophisticated system of majuscules and paragraphemic signs further accentuates these subdivisions. The poetic text in octaves is accompanied by Boccaccio’s marginal and interlinear commentary. The autograph manuscript also shows signs that Boccaccio had devised for the poem a rich visual and decorative apparatus (only partially executed).

The Teseida exactly replicates the number of lines of Virgil’s Aeneid. But it was Statius’s Thebaid—a twelve-book Latin epic on the fratricidal war between Oedipus’s sons Eteocles and Polynices—that provided the closest literary model. Boccaccio’s poem can be seen as both an epigonal continuation and an original expansion of Statius’s plot. The extensive authorial gloss (at Teseida 3.5) summarizing the plot confirms the attention Boccaccio devoted to the readers’ exact comprehension of both structural elements and specific passages.

The poem takes its cues from the closure of Statius’s Thebaid. In its first two books, the Teseida focuses on Theseus, the ‘duke’ of Athens: Book 1 deals with Theseus’s victory over Hippolyta, queen of the Amazons, whom he then marries; and Book 2 tells of Theseus’s victory over Creon, the sacrilegious king of Thebes. From the third book on, the poem is instead focused on the Theban warriors and war prisoners Arcita and Palemone, and their competing love for Emilia (Hippolyta’s younger sister). Theseus prompts a duel between Arcita and Palemone for Emilia’s hand. Arcita wins the duel, but Palemone survives. After marrying Emilia, Arcita dies of wounds from the duel. Funeral honors are performed and Theseus determines that Palemone and Emilia should marry. The poetry of arms of Books 1 and 2, in other words, gives way to the tradition of chivalric romance in Books 3 through 12.

Boccaccio’s project of an epic poem in the vernacular can be ascribed to the broader cultural project of authoring and canonizing vernacular literature. The Teseida’s concluding stanzas (12.84–86) are introduced by the rubric “Parole dell’autore al libro suo” (Words of the author to his book). Among these, the antepenultimate stanza has been almost unanimously perceived as a Dantean allusion. In the De vulgari eloquentia (2.2.8), Dante famously complains about the absence of martially-themed poetry in the Italian vernacular: “Arma vero nullum latium adhuc invenio poetasse” (As for arms, I find that no Italian has yet treated them in poetry). By singing the labors endured for Mars “in Italian” (12.84, 8: “nel volgar latio”), Boccaccio expects the Teseida to fill this void.

And Boccaccio gives his readers, in fact, what they could expect to find in an epic poem: invocations to the Muses (the poem’s incipit and the concluding sonnets), catalogs (Book 8), orations (Book 1), invocations and sacrifices to the gods (Book 7), arming scenes (Book 6), scenes of heroes at their finest in battle (Book 9), funeral games (Book 11), ecphrases (such as Book 7’s digressions on the Temples of Mars and Venus, or the description of the temple dedicated to Arcita by Palemone in 11.71–88), divine interventions ex machina (in Book 9 the Erinyes make Arcita fall off his horse), and theomachies.

The matter of Thebes and the martial topoi of classical epics, however, coexist in the Teseida with the eminently erotic component that Boccaccio derived from the troubadour and Tuscan love poetry traditions (here re-semanticized to praise monogamy and marriage over extramarital love). The disproportionate presence—for an epic poem—of the erotic matter (directly alluded to, after all, in the full title of the poem) and the somewhat mechanical juxtaposition of chivalric and classical elements have led scholars to regard the Teseida as a failed attempt at a poetry of arms in the Italian vernacular. Despite—or because of—a rich manuscript tradition (sixty-eight extant codices), an early editio princeps (Ferrara: Augustinus Carnerius, 1475), and a very influential rewriting (“The Knight’s Tale” in Geoffrey Chaucer’s Canterbury Tales), the modern audience of the Teseida consists, for the most part, of specialists.