This is an interesting concept for a book, and if you are a huge Grey's Anatomy fanatic I'm sure you'll like it. But it's a little redundant because the two halves cover essentially the same things, just from different perspecitive. And if you've *just* rewatched Grey's as I had before reading it, it might not be that entertaining either... of course, conversly, if you haven't seen Grey's in a while, a lot of the little jokes in the book might not make sense. I think it honestly works best as the website/blog that they have it running as now, where you can read the thoughts of 'Joe' and 'Debbie' in a more current format as you watch the show.
But by all means buy the book if you love Grey's as I do, because I did enjoy it.