As a milk man I was wondering why my customers aren't paying. Now I know. I need their money to upgrade from Platnum to Portfolio. This is Taken straight from L4 Home Page. 
We want to make sure it is crystal clear once more—this is probably not for you.
If you are happy with your existing library and never plan on buying a book again, just move along, there's nothing to see here. However, if you are like a lot of book lovers, and you realize that you are already spending your book budget, your travel budget, your kids education fund, your entertainment budget, and your milk money on more and more books—and have already spent thousands of dollars on books in the past few years—you would be crazy not to get this.
