Everyone's heard of C.S. Lewis's Chronicles of Narnia, but not as many have heard of his space trilogy. The first book is called
Out of the Silent Planet. It is about a man who is kidnapped and taken to Mars and meets the creatures there and has all kinds of adventures. In
Perelandra, he is taken to Venus to save that planet from falling into sin Garden-of-Eden style, and
That Hideous Strength is weaker on the time travel and such, but involves a creepy Institute that wants to deceive the world. Unfortunately, they are not available on Kindle yet, but, since the Narnia books have recently all been published for Kindle, I'm hopeful that they'll show up soon.
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Along those same lines, many of us probably read
A Wrinkle in Time, but Madeleine L'Engle's subsequent books about the Murray-O'Keefe family are also quite good. All involve one or more members of the family being pulled into some kind of adventure that culminates in confronting evil across space and time, or just in more ordinary ways. I think the next one chronologically would be
A Wind in the Door, in which Charles Wallace has contracted a mysterious illness and Meg and company must save him at the sub-cellular level.
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