While the buddy read is officially over, I continue to slowly make my way through The Crystal Cave in installments. I read a section and then reach for the other books I've got active before returning to Mary Stewart.
Book 4 - The Red Dragon picks up a bit compared to the previous sections and is my favorite so far. Merlin has a final reunion with his mother. Ambrosius conquers Britain for a brief moment and then succumbs to illness. Merlin helps with the conquest of Ireland and serves as the chief engineer to bring the king-stone from the Killare to the Giant's Dance at Amesbury (known in modern times as Stonehenge).