As I read this book, I kept thinking back to The Ugly Duckling. It may seem cliche, but that's exactly what's going on. Lexi is told she's ugly until she basically discovers wax and makeup. Then, BAM! Instant hottie.
Of course, there are other things going on at the same time to keep things interesting. Lexi discovers that, like herself, people aren't always what they seem-- and this has a wide range of complications for her.
I group Revenge of the Girl with the Great Personality under "beach reads" because it's a perfect read for when you don't want to think too deeply. It's quick and light. The characters are pretty straight forward, and I wouldn't say they undergo any overly drastic changes or growth. The dialogue is believable, so you get a good dose of contemporary fiction here. Also, at times there are snippets of wit and humor that will make you smile and maybe laughed inwardly, but nothing that will make you throw sand at your bestie in the chair next to you so that you can share what's on the page.