Book authors do not usually illustrate their books themselves. However, J.R.R Tolkien went on to illustrate his book, The Hobbit, to give his readers a better understanding. Most of the illustrations are maps that helped guide the reader about the many countries mentioned in the book. The other books mentioned do not have any illustrations or are illustrated by different illustrators.
For instance, John Tenniel illustrated Alice in Wonderland. Earnest H. Shepard, who also illustrated the Wind in the willows, illustrated Winnie-the-Pooh. However, the Hobbit was illustrated by its original writer J.R.R Tolkien in an attempt to explain the different worlds to the readers.