No April Fools Joke?
There's really a book for Amazon.com!
Amazon.com for Dummies. by Friedman, Mara. Hoboken, NJ : Wiley, c2004. You can learn all about the personalization services and how Amazon recommends items for you based on your searching and shopping preferences - wouldnt it be cool if the Library catalog did that?
Of special interest:
-Chapter 3: You Are the Master of Your Account
-Chapter 11: It's All About You!
-Chapter 12: Putting Your Two Cents In
You could just visit Amazon.com and check out how their recommendations feature works.