As self-realization gifts go, it's hard to beat a starship.
Norb Cortez trained most of his life for a colony-ship captain's berth. Didn't happen. None of the nine colony missions ever reported back. So, no more ships. He takes a dull job guarding freighters in Mars orbit.
Then a colony sends starship Aldebaran back. For him. He and his oddball pick-up crew go on a star-hopping adventure. They find and visit the old colonies, all of which have gone weird. Slowly they realize they must prevail against a trickster interstellar intelligence and return to Earth to perform a heavy duty.