It's definitely a cool idea, but the book did not execute it well. It turned into one of those books that's about high school kids, who they want to go out with, and all the other tiny things they do in their life. The future Facebook added an interesting element, but Emma ended up rushing home every day to check it, and ended up acting like kids do now, so it didn't seem different than the other books about a random high school kid. The idea wasted away as the book progressed, so by the end, it had lost any novelty that it had at the beginning.
The book is a 1.9. It's better than some books I've read, but not nearly as good as many others. Like Splenda, it seemed sweet at first, but quickly lost its appeal, and there are alternatives that are better.