Waterstones is the largest bookstore chain in the United Kingdom. The bookseller prides themselves positioning titles in the stores and online in order to assist people in discovering a brand new title. The company has gone beyond algorithms that monitor your website browsing behavior and is making active recommendations within their source code.
Many young web developers often look at a websites source code by using any popular internet browser and checking out what makes it tick. The Waterstones website actually has programming recommendations built right into the <head> element. Here is what you will see if you right click on the website and click on view source.
As you can see, there are names of books that have to do with programming and links where they can buy them. This obviously is meant to appeal to teenagers who want to learn more about programming for the web.