The Attention Merchants by Tim Wu.... Highly recommended!

“As one might gather from a painting of him scowling in a tall stovepipe hat, Day saw himself as a businessman, not a journalist. ''He needed a newspaper not to reform, not to arouse, but to push the printing business of Benjamin H. Day.''

Day's idea was to try selling a paper for a penny - the going price for many everyday items, like soap or brushes. At that price, he felt sure he could capture a much larger audience than his 6-cent rivals. But what made the prospect risky, potentially even suicidal, was that Day would then be selling his paper at a loss. What day was contemplating was a break with the traditional strategy for making profit: selling at a price higher than the cost of production. He would instead rely on a different but historically significant business model: reselling the attention of his audience, or advertising. What Day understood-more firmly, more clearly than anyone before him-was that while his readers may have thought themselves his customers, they were in fact his product.” 

― Tim Wu, The Attention Merchants: The Epic Scramble to Get Inside Our Heads