The minute I found out that the book was actually real and didn't just exist in the show, I had to buy it. The writers clearly put a lot of thought into this, and you can really hear Leslie's voice throughout, whether it be in her irrational admiratio nof Pawnee, or her addiction to JJ's waffles. There are also guest spots from other characters which are very funny, and spot on with how the characters act in the show.
Throughout, there's lots of humorous trivia about Pawnee which is good fun to read about. There's also a long list of MouseRat's previous names, so if that's not enough to convince you I don't know what is. It's just a shame the show is not shown on TV here, as Parks & Rec (season 1 aside) is probably the most consistent sitcom on air.
So if it isn't clear by now, treat yo self and buy this.