How does a book become well known?

The internet. Word of mouth is almost as fast as the speed of light with people from every class, race & nationality connected across the web. The internet has made middle class men billionaires because their product now has such a wide reach instantaneously.

Now you have librarians, people who work in bookstores & others who people listen to when they recommend books, & they have blogs, their on twitter, they have 30 followers. Followers blog & they tweet, their on facebook. If your product is good the world will hear about it.

They are good books. Unique to the present culture. Being new & fresh helps. Lord of the Rings revived because of the internet & the movies, they were new to many people. I did not hear about them until the movies were in the works. Before I read them, I searched the internet to see what people had to say, as I do for most everything before I buy.

Other then fifty shades of grey, the others have a catchy plot that appeal to lots of generations.

They appeal, they're something different, or the work well in the present climate they're realised in.