This ties nicely into her Planet Narnia book club reading:
The group has already finished discussing The Lion, The Witch, and The Wardrobe (imagery: Jupiter) and Prince Caspian (imagery: Mars), and they are now diving into The Voyage of the Dawn Treader (imagery: Sun). Serena is also totally drawn into the world of Percy Jackson, devouring the The Lightning Thief, the first book in the Percy Jackson and the Olympians series by Rick Riordan.
Another logical extension of this whole Greek myths craze is ancient history. We love the DVD series Drive Thru History with Dave Stotts. It covers Rome, Greece, Turkey, and Asia Minor, though we've been focusing most of our exploration on Greece.
Curious Kids Guides: Ancient Greece by Fiona Macdonald
Hail! Ancient Greeks by Jen Green
Alexander the Great by Demi
Find the Constellations by H. A. Rey
National Geographic Kids: 13 Planets by David A. Aguilar
Comets, Stars, the Moon, and Mars by Douglas Florian
The Planets by Gail Gibbons