If I were judging this book based purely off of the prologue it would be a perfect 5. Sanderson does an excellent job of setting up a vivid and interesting world where supervillians have emerged amidst the populace. The opening scene captured the comic book feel in a way no other book I've read has ever come close to replicating (and this element remained the strength of the book). Also, it was creepy. Unfortunately, for me, the book fell off significantly once I got into the meat of the story.
This is a teen book. Teenagers will love it. I, however, am not a teenager, and I wanted more depth. On the surface this book has lots of color and interesting ideas, but if you dig too deep at any one thing it starts to crumble. Details don't make sense, characters are one dimensional, plot points unravel, and so on. (Also, the fake swear words...just no. It's a pet peeve of mine when it is done poorly.) There were few (if any) surprises, and many of the revelations uncovered throughout the book left me somewhat disappointed. The romance angle also fell really flat for me, but your milage may vary.
Maybe I'm wanting too much. Maybe I set the bar too high. But if so that is only because the book started out so brilliant, and asking such interesting questions, that I felt compelled to dig in and really engage. So is it perfect? Far from. But it is a fast fun breezy read if that's what's on your agenda. If you want a summer comic book movie in novel format this is a good choice. It's in no way a bad book - it simply commits the sin of falling short of greatness when it so easily could have been.