This book, written by PR consultants tells you why your business is spending too much money on advertising and should spend money on PR instead.
Advertising lacks credibility. E.g., when I see an oil company billboard advertising their nature-loving 'green" activities, that doesn't convince me of much. Advertising does OK at reminding me that those companies exist, though.
This book's thesis is that if you have a new story to tell, you want to use P.R. There are journalists out there looking for new stories. They'd love to hear from you about your new whatsit.
But if you try to use advertising, then (a) you're telling people something new via a medium that they don't trust--they won't trust your story; (b) you're no longer "news" that a journalist can report--why bother to report something that's being advertised widely? So you won't get P.R.-ish publicity.
This book doesn't point out P.R.'s own credibility problems. Plenty of P.R. channels are losing credibility, too. Nowadays, a trusted news outlet is one that warns you where its message is coming from--investigative journalism involving checking more than one source is pretty sparse.
They also don't talk about highly-directed advertising; their criticism is for mass advertising. It's not clear what they think about, say, showing ads for fishing lures on Google searches for [trout]. (But this book was written back in 2002, so I guess that's excusable)