Specials (Uglies Trilogy Book 3) by Scott Westerfeld

Things never work out like Tally plans.  She wanted to be part of The Smoke, but the accidently brought Special Circumstances straight to The Smoke with her tracking device.  She wanted to think clearly, but the medicine she thought was supposed to help her severely hurt her friend.  She wanted to be with the guy of her dreams, but he couldn't forgive her.  In this third installment, Tally is now a member of Special Circumstances.  She's a member of an elite group of "cutters," who cut themselves for fun.  They have special tattoos and go on secret missions for Dr. Cable.  Tally thinks this is the life she has chosen, but always in the back of her mind is a nagging thought about David.  Where is he?  What is he doing? 

What would you be willing to do if the government told you to do something?  Would you do it and follow blindly?  Would you resist?  What if there were consequences for resisting?  This continues the struggle of free-thinking vs. societal rules, and it takes that struggle to new heights.  See what Tally does for those about whom she cares.  See what happens when the world they think they know changes.