I would characterise my understanding of science as reasonable, probably the kind of reader that
New Scientist is squarely aimed at; I've got the basics, I'm interested, and I'm genuinely excited about the
Large Hadron Collider getting switched on this week. As such, I am probably more clued up than Bryson's imaginary reader here, and I didn't learn many new ideas beyond his excellent description of the inner workings of a cell.
Where this overview really scores is in the many tales from scientific history. It is crammed with eccentric egomaniacs and unsung heroes, strokes of brilliance and selfless drudgery, all told with the author's familiar, breezy enthusiasm.
One dictum quoted late on regards the fate of major discoveries and rings all too true:
First they don't believe you, then they tell you it isn't important, then they credit the wrong person.