These are by the husband and
wife team of illustrators,
Ingri & Edgar Parin D’Aulaire.
The first is the D’Aulaires’ Book of Norse Myths, original copyright 1967 and renewed in 1995 by family members. My copy was a gift from one of my sisters. The end papers show a map of The 9 Norse Worlds.
And on my bookshelf, another book with pictures by the D’Aulaires. This one is The Lord’s Prayer, published in 1943 by Doubleday, Doran & Company.
I originally thought all the illustrations used colored pencils. However, the flap of the Norse books says “originally they used stone lithography for their illustrations. A single four-color illustration required four slabs of Bavarian limestone that weighed up to two hundred pounds apiece. The technique gave their illustrations an uncanny hand-drawn vibrancy.” They used the technique until the early 1960’s when the process became too expensive and then switched to another technique that approximated the texture of lithographic stone.