If the Beowulf manuscript is not the author's autograph (the author's own handwriting), as claimed by Kevin Kiernan, then the first critical appreciation we have of the poem is the manuscript itself. Someone thought enough to copy it down or to have it copied on good vellum by two fairly good scribes—incuring a sizable expense for the year 1000. Another indication of early popularity may be in its apparent influence on another Old English poem, Andreas, which survives in a manuscript kept at Exeter Cathedral in Devon since the mid-eleventh century. After that there is no sign of the poem for well over five hundred years.

Laurence Nowell acquired the eleventh-century manuscript in the 1560s and wrote his name and date on the top of the first page. The manuscript eventually appeared in the library of a family named Cotton, but it does not appear in either of the library's two catalogues (1628-29 and 1696). In 1704, Humfrey Wanley, however, recorded it in his published catalogue of manuscripts containing Old English. A century later Sharon Turner published illustrative citations and very inaccurate translations. The effective rediscovery of the poem was the work of an Icelander, G. S. Thorkelin, and a Dane, N. S. F. Grundtvig. Thorkelin had a transcription of the poem made and made a second himself. He published his edition in 1815. Grudtvig worked on and published an edition of the poem between 1815 and 1861. Perhaps the greatest single scholar of the poem, Grudtvig proposed many of the now accepted restorations of the text (emendations) and proved that Beowulf's uncle Hygelac was in fact a historical figure. For Grundtvig the poem's greatness lay in its sense of moral purpose. He approached the poem as a unified work of literature in its own terms, anticipating the major topics of modern Beowulf criticism.

After Grudtvig, scholars concentrated on clearing up problems of the poem's language and allusions. Others mined the poem as a historical and social document in the hopes of proving their often politically inspired theories about ancient Germanic life. Still others attempted to identify still older poems (lays) within it or to discover a nature myth or allegory in its action. By the opening years of the twentieth century, Beowulf was a synonym for undergraduate literary boredom. In 1915, novelist D. H. Lawrence used it in The Rainbow as a symbol of aridity and meaninglessness in education. Robert Graves just back from front-line battle in World War I in 1919, disagreed: "Beowulf and Judith [another Old English poem] seemed good poems to me. Beowulf lying wrapped in a blanket among his platoon of drunken thanes . . . all this was closer to most of us at the time than the . . . eighteenth century."

It was another returned soldier, J. R. R. Tolkien, who, in writing "Beowulf: The Monsters and the Critics," made it impossible to treat the poem simply as a resource for the study of language or anthropology. Some thirty years earlier, W. Kerr had complained that the monsters cheapened the poem. Tolkien insisted that the evil which the monsters represented was a central part of a profound commentary on the human condition. Many critics agree that Tolkien redirected readers of Beowulf from what the poem is not to what it is. His powers as a writer, not only in his lecture but also in his use of Beowulf in The Lord of the Rings, mean that Beowulf came to be accepted not only as literature, but as great literature.

Criticism in the 1930s was dominated by discussions of lyric poetry. Tolkien's elegiac reading of Beowulf although not entirely convincing in its details, was popular among critics, and re-focused critical attention away from the problems of narrative momentum and on to the poem's humanity. Although F. Klaeber had established the poem's essential Christianity over twenty years before, critical tendencies were also now sympathetic to Tolkien's identification of a Christian reading beneath the surface action. The horrors of war, too, had made monstrous and unreasoning evil at the heart of the human situation a compelling subject.

Klaeber saw Beowulf as a real, even Christlike, hero. Tolkien, like many writers and film makers of the middle of the century, was uncomfortable with "traditional" heroes. Eric Stanley, John Leyerle, and others developed a vision of the man Beowulf flawed by his desire for praise or treasure or even being born before the arrival of Christianity. Leyerle and Halverson, and even more thoroughly Berger and Leicester, tend to relocate the flaw from the character to his society. In its most developed form, this view says that the heroism the characters see as necessary for personal worth and social solidarity are destructive of both. These studies are often selective in their presentation, out of touch with historical reality and full of special pleading. In them Beowulf is, as the saying goes, "damned if he does and damned if he doesn't." Kemp Malone and others rebutted at least the more extreme of these arguments.

Many recent readers have struggled with the assumption that since Beowulf is not Christian the poet must have assumed that he was damned. This does not seem to fit with what actually goes on in the poem. Some critics have flirted with the idea of a slightly heretical or at least theologically confused poet. For much the same reason, Margaret Goldsmith proposed an allegorical reading of the poem. More recently, beginning with a collection of articles edited by Colin Chase in 1981, Beowulf criticism has been refocused on the manuscript itself and the question of dating. In the last fifty years hundreds of articles and books have been written on Beowulf, of them perhaps the most influential have been Adnen Bonjour's 1950 The Digressions in Beowulf, E. B. Irving's two books A Reading of Beowulf (1968) and Rereading Beowulf (1989); and John Nile's Beowulf: The Poem and its Tradition (1984).