Not sure it's fair to rate an astronomy book that predates the moon landing. This is early Sagan, but already shows his signature style. As usual, Sagan shares details about the science and letting them speak for themselves, not trying to be cute or funny. Sagan is honest about what is known and what is theoretical and what could be possible to learn in the future as crewed and uncrewed space travel advances. And he was right about that.
And I'm guessing this is the first time that Sagan describes his "gasbags" -- a fanciful idea of what life in Jupiter's atmosphere might be like.