I read it, it was ok. But, if you've watched the show, you probably won't learn much new. I'd only read it if you're bored and have nothing else to read.
I read it and felt the same as Jezebel. Also, it was a little too closed for me, I wanted them all to be a bit more real about their conflicts and such, but they were very vague and "we're working on it".
Some of the stuff they talk about was revealed in a q&a episode. It's hardly thrilling stuff, but I was curious (and got the book from the library). And it did give me a different perspective on them since there is a bit more info about their early dynamics and so forth. It improved my opinion of Robyn but also made pretty sad for all of them.