Call it lucky number twenty-one. Here’s a tidbit from the latest Amazon review:  

The ebook is free right now but THE FEVER won’t be free forever, so take advantage of this special offer. 

http://www.smashwords.com/books/view/557754

Enter coupon code “SFREE”
Warning:  the sequel is coming soon, if you catch The Fever now you WILL NOT BE ABLE TO RESIST “A Curse That Bites Deep”