If you were captivated by the sweeping timescales in Last and First Men, you'll find The Book of the New Sun enthralling. Wolfe's masterpiece follows Severian across a far-future Earth, blending mythic grandeur with a haunting sense of civilizations rising and falling over aeons. The narrative's ambition and reach echo Stapledon's speculative audacity.

If you were fascinated by Stapledon's imaginative leaps through countless human species, Diaspora offers a similarly mind-bending journey. You'll follow posthuman, digital, and biological entities as they adapt and branch across the galaxy, raising profound questions about identity and what it means to be human.

If you enjoyed pondering humanity's place in the cosmos and its ultimate fate, Childhood's End will resonate with you. Clarke's novel traces the final chapter of the human species under the guidance of mysterious Overlords, exploring transcendence, loss, and the evolution of consciousness in a manner reminiscent of Stapledon's sweeping vision.

If Stapledon's intricate depiction of future civilizations appealed to you, you'll be drawn to The Dispossessed. Le Guin builds two contrasting worlds, Anarres and Urras, with rich histories, languages, and philosophies, allowing you to immerse yourself in profound social speculation.

If you relished the big ideas and speculative reach of Last and First Men, Solaris offers a cerebral exploration of contact with a truly alien intelligence. Lem's novel combines philosophical musings with a haunting narrative about humanity's limitations in understanding the cosmos.