the same year, he began compiling his poems of most interest to children into a new book entitled "rhymes of childhood". the book was richly illustrated by howard chandler christy, and riley wrote a few new poems for the book under the pseudonym "uncle sydney." "rhymes of childhood" became riley's best selling book, and sold millions of copies. it has remained in print continually since 1912 and helped earn him the nickname the "children's poet". even riley's rival, clemens, commented that the book was "charming" and made him weep for his "lost youth".