I read Purple Cow on a quick trip. During the trip my wife went to a Japanese book store in LA that sells used books for $1 each. In the pile of books she found The Complete Manual of Suicide and immediately had to buy it.
This book is an example of a Purple Cow. Something remarkable that compels certain people to evangelise the product. In this case the book also caused a furor. My wife was a teenager and wasn’t able to buy it or even read it. Through word of mouth alone she wanted it. She desperately wanted it but it wasn’t available for 18 years.
The book just contains a very encyclopedic list of suicide methods. Success rates, pain, etc. As she was telling me about her excitement in finding the book I questioned her motivations. I knew that it was the Streisand Effect and she really had no interest in the information. Her interest was purely in the word of mouth marketing and controversy.
That interest kept hold and as she entered a book store 18 years later she felt compelled to buy it. And it was only a dollar.