Interesting Recommendation

I received an email from Amazon today, with the following recommendation in it:

Dear Amazon.com Customer, We've noticed that customers who have purchased or rated books by Aristotle have also purchased If You Got It, A Truck Brought It: Our First Adventure by Robin Smith. For this reason, you might like to know that If You Got It, A Truck Brought It: Our First Adventure is now available.  You can order yours for just $8.99 by following the link below. If You Got It, A Truck Brought It: Our First Adventure  Robin Smith  Price: $8.99     Product Description With bright colorful illustrations and adorable characters, Josie and her freewheeling friends take you on an adventure to learn how a book is made.Along the way we'll get a start on learning colors, numbers and the alphabet.

 

Notice the basis of the recommendation: because I'd purchased books by Aristotle, they recommended a particular children's book. I smell a statistical cluster in there somewhere.