Classic 4/5
Solar survey vessel commander Norton is assigned to check out a deep space object that has entered our solar system, only to discover it is in fact a space ship from an unknown civilization far beyond Pluto. Okay, it’s years since I read this book but it sticks in my memory—I loved it. The premise was plausible, giving a science-fictional-suspension-of-disbelief, the crew’s explorations were enchanting, and the ending was clever and unexpected.