Christopher as an academic
Christopher as a contributor to Middle-earth
- Drew the maps for The Lord of the Rings, (and later, for The Silmarillion, Unfinished Tales, etc.)
- Wrote the chapter "Of the Ruin of Doriath" for The Silmarillion.
- Edited over twenty volumes of his father's writings.
- For more on this topic, see Vincent Ferré's "The Son Behind the Father: Christopher Tolkien as a Writer" (The Great Tales Never End, 2022), which makes the case that Christopher should be considered a writer in his own right, and that his contributions to Middle-earth qualify as literature.
Christopher as a letter writer
Christopher Tolkien was certainly the most intelligent, most insightful, most engaging, and wittiest person I have ever had the pleasure to meet and correspond with, and I bet the same is true for many others. A “letter from Christopher” was always a special occasion of anticipation and pleasure. I of course could never match him as a correspondent, not even close; but that didn’t matter to him: he nonetheless genuinely cared about and engaged my thoughts, questions, and concerns, because we shared so many goals and concerns in common.
Christopher's posthumous works
It should also be known that in Christopher's will, he makes mention of (possible) unreleased writings of his which he gives the publishing rights of to his wife:
... the ownership (tangible and intangible) of all my archives, writings, manuscripts or typed documents, complete and incomplete works of my creation with task of making use of them in a way she judges appropriate in the interests of my work's moral rights, ... to take control of my archives (preparatory notes, reading notes, outlines, drawings, plans, drafts, letters or handwritten documents, typescripts, annotated manuscripts, proofs, finalised manuscripts, correspondence, electronic files, on all media ... ); ... to decide on the release and publishing of works which have not been released at the time of my death;
It is thus possible that more writing from Christopher will be published in the future.
(These are fairly comprehensive and help show that Christopher did not write any of his own traditional non-academic fiction books unrelated to Middle-earth.)