The main premise is that the media is absolutely terrible at informing the public on issues relating to science. Goldacre (himself an NHS physician in the UK) skewers the press for fear mongering, relying on frauds or shysters as "experts", supporting pseudoscience and a whole host of other information atrocities. His focus is entirely on the UK and the personalities and media sources he discusses will be unknown to US readers (like me), but that doesn't get in the way of his anecdotes or points.
A particularly amusing highlight from the text was this graph...
Which points to the dangers of incompetence; the least able are also the least likely to know it. If you don't have time to read the book you still might want to check out Ben's Bad Science blog.