It's always been fascinating to me that a physics geezer (Freeman Dyson) took the idea from more ancient geezer Olaf Stapledon's 1937 'Star Maker'. It is a quasi-spiritual story that has our protagonist wrestled from his humanly shell for a tour of the cosmos and he gets to meet the Maker and Creator who is, for all intents and purposes, a nerd!<p>The best way to easily get a handle on Stapledon's works over deep time is to look for a compendium hardcover "To The End Of Time" which has always been a treasured book in my family.<p>Also of note in adventure/fantasy, did you enjoy Verne's "Journey to the Center of the Earth" as a kid but were a bit disappointed that the narrative elements moved the story along a bit too quickly and so much of the underworld was left unexplored? Try an edition of "Etidorhpa" with the Knapp illustrations. Lots of imagination fuel and exploration in a hollow Earth setting.