As you may have noticed, I've been into reading books in three-somes recently. This is purely by default, I assure you, I do enjoy a good stand alone book as well.
The Uglies trilogy by Scott Westerfeld was very enjoyable. They take place several hundred years after the demise of our civilization, in a world where at the age of sixteen everyone undergoes major cosmetic surgery and is transformed from an Ugly to a Pretty.
Tally Youngblood is an excellent main character who seems human enough to make the story plausible. Without giving too much away, the trilogy follows her fight to just be herself. I found myself mad at her at the end of the second book, but was pleased with the ending of the third.
There is a fourth book, but I believe that it takes place in the same world, but with different characters.