ISAN is YA sci-fi romance. I bought my copy brand new.
Review:
After her mother's death, Ava ended up in foster care, and then juvenile detention. Her life might have continued on a downward spiral if it weren't for Russ's arrival. He selected her to join ISAN (International Sensory Assassin Network), a secretive organization that supposedly helps the world by quietly assassinating particular people. Not that Ava knows much about the reasons behind her assignments. She does as she's told because she doesn't really have any other choices - ISAN is her only home now, and she can't leave except for brief recreational outings in which she and the others on her team are always closely watched.
Ava and her team complete regular "mental missions," virtual reality practice missions in which the girls accustom themselves to fighting and killing, achieving particular goals within time limits, and, most importantly, learning how to use their HelixB77 serum-enhanced senses and abilities. The serum makes them stronger, faster, and more fearless. It also gives certain girls, Ava included, special abilities - Ava can see a map of her surroundings in her head and, occasionally, dots that tell her where certain things and people are located.
Ava's world is thrown into disarray when she's somehow contacted by a guy who calls himself Sniper. She's intrigued by him (honestly, she's intrigued by anyone male who either is or might potentially be attractive) but also wary, because no one from the outside world is supposed to be able to contact anyone in ISAN or vice versa. When she finally meets Sniper, she's left with more questions than answers. He claims that they used to know each other, but if that's true, why doesn't she remember him?