here and here. There is not much more to be said.
This book cover illustrates the battle on the surface of the proto-planet but a more interesting image would have been that of a spaceship dwarfed by the caverns of the Sky Cave as it finds its way through and between them.
Reading some of his earlier and later stories in quick succession demonstrates Anderson's maturation as a writer. I think that "Duel on Syrtis," describing single combat between two beings in the Martian desert, is a better written work than its sequel, "War-Maid of Mars," with its chase scenes, escapes, armed agents in cars etc.
"Lord of a Thousand Suns" has features in common with the History of Technic Civilization - an interstellar civilization overthrown a million years ago, the idea of a helmet which, when worn, imposes the recorded pattern of a long dead personality onto a living brain. However, this story's Flash Gordon action-adventure fiction contrasts sharply with the subtlties of The Day Of Their Return, a novel that evokes the religious yearning of a planetary population awaiting deliverance by the Ancients when They return, soon...