Looking for the name of an old series of books....?

I loved this series when I was little, and my mother had then all. They had a bright orange binding and came in a set like encyclopedias. Each one had a theme. I remember that there was a science, poetry, Greek literature, folk stories, fairy stories, and history volume. There may have been more, but I cannot remember. They were written for children and young adults, and I suppose there were about 20 in the set. If ANYONE recognizes this and could give me a clue, I would be infinitely grateful. I would ask my mom, but she ped away about 3 months ago and now I am hell-bent on finding these books. Thanks!