Agent G4 books in series
Agent G Publisher's Summary
In a world where virtually any death can be bought for the right price, follow the path of a high-tech assassin searching for answers to questions he shouldn't be asking along with his next target. Agent G is a Letter, one of the Society's 26 weapons for hire.
Unfortunately for the Society, G is starting to think for himself.
Unfortunately for G, he's in the middle of infiltrating a rival organization and is running out of people he can trust.