The son of the author and academic J. R. R. Tolkien, Christopher edited 24 volumes based on his father's posthumously published work, including The Silmarillion and the 12-volume series The History of Middle-Earth, a task that took 45 years.

They have further noted that his additions to The Silmarillion, such as to fill in gaps, and his composition of the text in his own literary style, place him as an author as well as an editor of that book.

[4] He won a place to study English at Trinity College, Oxford, still aged 17, but after a year and a half there he received his call-up papers for military service.

[5] Tolkien was for a long time part of the critical audience for his father's fiction, first as a child listening to tales of Bilbo Baggins (published as The Hobbit), and then as a teenager and young adult offering feedback on The Lord of the Rings throughout its 15-year gestation.

[5] Away from his father's writings, he published The Saga of King Heidrek the Wise: "Translated from the Icelandic with Introduction, Notes and Appendices by Christopher Tolkien" in 1960.

Christopher organised the masses of his father's unpublished writings, some of them written on odd scraps of paper half a century earlier.

[12] He explained: By the time of my father's death the amount of writing in existence on the subject of the Three Ages was huge in quantity (since it extended over a lifetime), disordered, more full of beginnings than of ends, and varying in content from heroic verse in the ancient English alliterative metre to severe historical analysis of his own extremely difficult languages: a vast repository and labyrinth of story, of poetry, of philosophy, and of philology ... To bring it into publishable form was a task at once utterly absorbing and alarming in its responsibility toward something that is unique.

[13] Noad adds that "The whole series of The History of Middle-earth is a tremendous achievement and makes a worthy and enduring testament to one man's creative endeavours and to another's explicatory devotion.

The Legend of Sigurd and Gudrún appeared in May 2009, a verse retelling of the Norse Völsung cycle, followed by The Fall of Arthur in May 2013,[18] and by Beowulf: A Translation and Commentary in May 2014.

[19][20] Vincent Ferré comments that early in the process of editing his father's unpublished writings, "the real nature of Christopher Tolkien's work was a matter of debate, before a more simplistic consensus began to prevail.

"[21] Christopher Tolkien explained in The Silmarillion's foreword in 1977 "I set myself therefore to work out a single text, selecting and arranging in such a way as seemed to me to produce the most coherent and internally self-consistent narrative.

"[21][22] In 1981, the scholar of literature Randel Helms, taking that statement as definitive of Christopher Tolkien's editorial, indeed authorial, intentions:[21] stated in terms that "The Silmarillion in the shape that we have it [a single-volume narrative] is the invention of the son not the father".

[24][a] Ferré records that, much later, in 2012, Christopher Tolkien admitted "I had had to invent some passages",[26] that he had had a dream that his father was anxiously searching for something, and that he had "realized in horror that it was The Silmarillion.

He gives two reasons for this: that The Silmarillion reveals his own writing style and "the choices he made in 'constructing'" the narrative; and that he had to devise parts of the story, both to fill gaps and when "threads were impossible to weave together".

[21] Christopher Tolkien's editing of the 12 volumes of The History of Middle-earth, using his skill as a philologist, created an editorial frame for his father's legendarium, and for the books derived from it.

[37][38] He felt that The Lord of the Rings was "peculiarly unsuitable for transformation into visual dramatic form", whilst his son became involved as an advisor with the series.