 Though he did some oil paintings, Brooke was best known as a book illustrator.WorldCat library records show that he illustrated several works by Mrs. Molesworth in the mid-1890s, perhaps from 1892; one was "The Carved Lions" (1895) in its first edition.His skillful and witty illustrations in Andrew Lang's "Nursery Rhyme Book" (1897) established his reputation as a leading children's book illustrator of pen-and-ink line drawings and watercolors.