The Birth of the Assassin brings you back in time from The Heart of an Assassin and I really feel you will like the story better if you read that one first. Heart will lose some of its punch if you read Birth first, no matter if that seems backwards.
The Birth of an Assassin takes us through the life of Theo, how he becomes an infinitesimally good shot and how choices he makes shadow his life forever, his regrets, his associations, and friends.
Though the dialogue is not heavy in this book, the author conveys how the characters meld and feel in other ways, it has a very masculine feel to it (not saying women won't enjoy it, but that men may enjoy it more).
eBook The Birth of an Assassin