Two great early space opera novels, Brigands of the Moon (1930), and its sequel, Wandl, the Invader (1932) in which Gregg Haljan saves the world first from space pirates and then from space invaders.
In this sequel to “Brigands of the Moon”, Gregg Haljan tries to save the Earth, Mars and Venus from being destroyed by the giant brains of the planet Wandl.
A Million Years In The Future – a thrilling interplanetary story of Jan, the last man on Earth; Tara the Glorious, Queen of the Stars; the Wolves of Worra, the Nine Terrible Sisters, and the Black Raiders, destroyers of a thousand planets.
Skylark Three by E.E. ‘Doc’ Smith is the second book of the classic Skylark trilogy. Skylark Three is “the tale of the galactic cruise which ushered in Universal Civilization.”