Money is where ideas thrive. I would build something based on recommendation based on users who you like. I like someone and I want to know the books they like

Money is where ideas thrive. I would build something based on recommendation based on users who you like. I like someone and I want to know the books they like and more and more of this. so essentially Facebook for Book recommendation. I know someone and so I know what books they read. User can choose to publicize the recommendation or to certain group of people or private.