Classic science fiction.
This book was always one of my favorite Heinleins. Although it was written for young readers, it still has the charm of early science fiction that can capture an adult's imagination.
Athentic oldie from the master
This throws me back to a reading list from the seventh grade. There it sat since the early 1950s. Now I find it at a library used book sale. I rescue it from the discard pile. Why not give it a shot? It turns out that the principal characters might have been cousins to the Hardy Boys who uncover a plot and set out to rescue the Earth colony on Mars from annihilation. This is a good book for teenagers and a suitable introduction to science fiction: not overpowering in scientific detail, with interesting but sketchy exposure to technological advancement, and certainly conjuring up some odd alien lifestyles.
