"And yet it moves" was Galileo's sotto voce remark, after the Church forced him to recant his statements about the Earth moving around the sun. Loeb criticizes astronomers who assert that Oumuamua's non-gravitational movement was due to outgassing, despite no visible evidence of outgassing.

The core idea of this book is that other astronomers freely admitting that no visible outgassing was detected, are nevertheless committed to the explanation and unreasonably refuse to consider other possibilities. Loeb's favorite possibility is that solar radiation pressure explains the acceleration, if Oumuamua is a thin mass, like the lightsails we've designed on Earth. He's coy about committing to alien construction of such a sail, but states it as a possibility.

Overall, the book is longer than it needs to be, and contains more autobiographical material than I like, but I do appreciate the sentiment that Science has to be open-minded and follow the data to wherever it leads, rather than prematurely pruning leads. Denying the possibility of it behaving like a lightsail simply because "it's never aliens" is intellectually lazy.