Saving the world as well as all of its grown-ups sends middle schooler Mars and his buddies between planets as well as dimensions in this podcast-novelization wrap-up.In a plotline that has a strong sense of "making this stuff up as we go," Mars completes his escape from the all-child Mars Colony-with a folded-in side venture to an alternate world where everyone he knows has turned creepy and staring-but returns to an Earth that has been set on the path to environmental recovery and worldwide democracy by kids because (not creepy at all) the adults have disappeared. What with plenty of preteen banter, the odd hidden lab or space portal to discover, parent issues to work out, and, best of all, a greatly increased role for the giant fuzzy tardigrades met in previous episodes, there's plenty for readers willing to go with the flow to enjoy, and, along with frequent locale switches, quick progressions from one crisis to the next keep the pacing snappy. In the end, an arbitrary blanket reset not only restores the grown-ups, but brings the entire story back to the first volume's opening scene…only in better, improved versions of middle school and the world. Aside from India-born Mars and his loving Mamaji, diversity in the cast is cued mostly by names; there are two significant nonbinary characters.A fun, if slapdash, journey through space, time, and preadolescence comes to a shiny ending. (Science fiction. 10-13)