The set of commentaries on the works of Virgil (Vergil) entitled In tria Virgilii opera expositio or Commentarii in Vergilii opera by the late fourth century to early fifth century Roman grammarian Maurus Servius Honoratus (Servius) remain the only complete extant edition of a classic author written before the collapse of the western Roman empire. That this particular critical edition was preserved through the Middle Ages was undoubtedly a result of the signal importance attributed to Virgil by medieval Christian scholars who viewed Virgil's Aeneid as foreshadowing Christ, reinforcing the central importance of the Aeneid for the teaching of Latin. Servius's work was organized very much like a modern edition, and was based partly on an extensive Roman Virgilian critical literature, much of which is known only from the fragments and facts preserved in his commentary.
"The commentary on Virgil (Latin: In Vergilii Aeneidem commentarii) has survived in two distinct manuscript traditions. The first is a comparatively short commentary, which is attributed to Servius in the superscription in the manuscripts and by other internal evidence. A second class of manuscripts, all deriving from the 10th and 11th centuries, embed the same text in a much expanded commentary. The copious additions are in contrast to the style of the original; none of these manuscripts bears the name of Servius, and the commentary is known traditionally as Servius auctus or Servius Danielis, from Pierre Daniel who first published it in 1600. "The added matter is undoubtedly ancient, dating from a time but little removed from that of Servius, and is founded to a large extent on historical and antiquarian literature which is now lost. The writer is anonymous and probably a Christian", although he is not, as is often suggested, Aelius Donatus. A third class of manuscripts, written for the most part in Italy, gives the core text with interpolated scholia, which demonstrate the continued usefulness of the Virgilii Opera Expositio" (Wikipedia article on Maurus Servius Honoratus, accessed 08-12-2014).
The usefulness of Servius's work for the teaching of Virgil undoubtedly motivated the production of five 15th century printed editions, of which the first may have been issued in Rome by Ulrich Han "about 1470-71" (ISTC No. is00478000). Another edition was issued from Strassburg by Adolf Rusch, the "R-Printer" "not after 1471" (ISTC No. is00480000). An edition issued by Bernardus and Dominicus Cenninus of Florence, and edited by Petrus Cenninus, was issued, according to its three colophons, on 7 November 1471, 9 January 1471/72, and 7 October 1472. (ISTC No is00481000). This was probably the first book printed in Florence.