Their most collectible book to date is Enid Blyton's 1979 Dean book, called, The Enchanted Wood.
When I was about 10 or 12 years old I was given a book , Tales Of Ancient Greece, written by Mae Broadley and illustrated byAnne and Janet Grahame Johnstone.
The illustrations were quite magical and actually encouraged me to read the stories. It was a book written for children and the stories were adapted from classic Greek Mythology for a younger audience but it was the images contained within that made this a cut above most children's books. I had not seen illustrations quite like these before and the impact stays with me even today. I later becam aware of the Johnstone's celebrated work for Enid Blyton's The Enchanted Wood, but it was their work on Greek mythology that remains my personal favourite of all their work.