First off, let me just say this: I loved "Cinder". As of right now, it's still holding the spot as my favorite book this year.
When I'd heard about the prequel, I was excited. It's nice to be able to see what happened to Cinder before she meet Prince Kai, and to be able to gain a better understanding as to what happened to the man (Garan) who brought Cinder home. Meyer makes sure to give you a better insight without revealing too much within these 17 pages.
I always make sure to read the prequels of a book I enjoyed, and well, I'll just say this: this one is nearly as good as the novel itself. Yes, within seventeen pages Meyer manages to pull the reader in just as easily as she does with "Cinder".
You can either read the prequel on Tor's site, or you can purchase the e-book for $0.99!