I needed the explanation:

Storytelling icon J.R.R. Tolkien (January 3, 1892–September 2, 1973) was also among those rare creators with semi-secret talents in a discipline other than their primary realm of fame — but while his original sketches for the first edition of The Hobbit have seen the light of day in recent years, few realize that Tolkien, who self-illustrated many of his famous works, was as much an artist of pictures as he was of words. Unlike other famous authors who also drew but only as a hobby or diversion, including Sylvia Plath, William Faulkner, andFlannery O’Connor, Tolkien approached the visual medium with as much thoughtfulness and imaginative rigor as he did his stories. J.R.R. Tolkien: Artist and Illustrator (public library) collects more than 200 color reproductions, many previously unpublished, of Tolkien’s surviving art in watercolor, pencil, and ink, spanning sixty years of his life — from his childhood drawings to his illustrations for his books to his final sketches, as well as the drawings he created for his own children, his obsessive calligraphy, and his imaginative maps of Middle Earth.

Wayne G. Hammond and Christina Scull, who edited the volume and who ventured to England to find the exact locations where each of Tolkien’s drawings was created, write in the introduction:

We have long felt that Tolkien’s art deserves to be as well known as his writings. The two were closely linked, and in his paintings and drawings he displayed remarkable powers of invention that equalled his skill with words. His books have been read by countless thousands; most of his art, however, has been seen by only a very few.

Fortunately, a wealth of Tolkien’s art survives, for the beloved author seems to have had “an archivist’s soul,” as Hammond and Scull aptly put it: He kept nearly everything he drew, down to the scraps of paper filled with spontaneous doodles, and carefully tucked his most prized creations into special envelopes which he opened periodically to add captions and inscriptions years after the drawings were made.