I'd heard about the golden ratio from TV programs and wanted to find out more, in particular about the aspects related to beauty and proportion. However, much of the start of the book seemed to be spent discussing where this number may or may not have first been discovered, and in disproving a number of theories about who may or may not have been aware of it. I didn't find this very interesting, though the background on the history of mathematics might be of general interest.
The more factual bits of the book were more engaging, but it didn't really seem to have any new material or go into a huge amount of depth. There wasn't anything that had a real punch, and at the end I felt there were still a lot of questions unanswered.