Including Troilus and Criseyde, House of Fame, and Parliament of Fowls, The Canterbury Tales is near-unanimously seen as Chaucer's magnum opus

including Troilus and Criseyde, House of Fame, and Parliament of Fowls, The Canterbury Tales is near-unanimously seen as Chaucer's magnum opus. He uses the tales and descriptions of its characters to paint an ironic and critical portrait of English society at the time, and particularly of the Church. Chaucer's use of such a wide range of classes and types of people was without precedent in English. Although the characters are fictional, they still offer a variety of insights into customs and practices of the time. Often, such insight leads to a variety of discussions and disagreements among people in the 14th century. For example, although various social classes are represented in these stories and all of the pilgrims are on a spiritual quest, it is apparent that they are more concerned with worldly things than spiritual. Structurally, the collection resembles Boccaccio's Decameron, which Chaucer may have read during his first diplomatic mission to Italy in 1372.

It has been suggested that the greatest contribution of The Canterbury Tales to English literature was the popularisation of the English vernacular in mainstream literature, as opposed to French, Italian or Latin. English had, however, been used as a literary language centuries before Chaucer's time, and several of Chaucer's contemporaries—John Gower, William Langland, the Pearl Poet, and Julian of Norwich—also wrote major literary works in English. It is unclear to what extent Chaucer was seminal in this evolution of literary preference.

While Chaucer clearly states the addressees of many of his poems, the intended audience of The Canterbury Tales is more difficult to determine. Chaucer was a courtier, leading some to believe that he was mainly a court poet who wrote exclusively for nobility.

The Canterbury Tales is generally thought to have been incomplete at the end of Chaucer's life. In the General Prologue,[5] some 30 pilgrims are introduced. According to the Prologue, Chaucer's intention was to write four stories from the perspective of each pilgrim, two each on the way to and from their ultimate destination, St. Thomas Becket's shrine (making for a total of about 120 stories). Although perhaps incomplete, The Canterbury Tales is revered as one of the most important works in English literature. It is also open to a wide range of interpretations.

The question of whether The Canterbury Tales is a finished work has not been answered to date. There are 84 manuscripts and four incunabula (printed before 1500) editions[7] of the work, dating from the late medieval and early Renaissance periods, more than for any other vernacular English literary text with the exception of The Prick of Conscience. This is taken as evidence of the Tales' popularity during the century after Chaucer's death.[8] Fifty-five of these manuscripts are thought to have been originally complete, while 28 are so fragmentary that it is difficult to ascertain whether they were copied individually or as part of a set.[9] The Tales vary in both minor and major ways from manuscript to manuscript; many of the minor variations are due to copyists' errors, while it is suggested that in other cases Chaucer both added to his work and revised it as it was being copied and possibly as it was being distributed. Determining the text of the work is complicated by the question of the narrator's voice which Chaucer made part of his literary structure.

Even the oldest surviving manuscripts of the Tales are not Chaucer's originals. The very oldest is probably MS Peniarth 392 D (called "Hengwrt"), written by a scribe shortly after Chaucer's death. Another famous example is the Ellesmere Manuscript, a manuscript handwritten by one person with illustrations by several illustrators; the tales are put in an order that many later editors have followed for centuries.[10][11] The first version of The Canterbury Tales to be published in print was William Caxton's 1476 edition. Only 10 copies of this edition are known to exist, including one held by the British Library and one held by the Folger Shakespeare Library.

In 2004, Linne Mooney claimed that she was able to identify the scrivener who worked for Chaucer as an Adam Pinkhurst. Mooney, then a professor at the University of Maine and a visiting fellow at Corpus Christi College, Cambridge, said she could match Pinkhurst's signature, on an oath he signed, to his handwriting on a copy of The Canterbury Tales that might have been transcribed from Chaucer's working copy.[12][13] Recent scholarship has cast severe doubt upon that identification.

In the absence of consensus as to whether or not a complete version of the Tales exists, there is also no general agreement regarding the order in which Chaucer intended the stories to be placed.[15][16]

Textual and manuscript clues have been adduced to support the two most popular modern methods of ordering the tales. Some scholarly editions divide the Tales into ten "Fragments". The tales that make up a Fragment are closely related and contain internal indications of their order of presentation, usually with one character speaking to and then stepping aside for another character