There are some issues with the writing in this novel. First, and this is mostly a stylistic preference, he writes in present tense. That can work to lend a sense of immediacy. I've seen it used to good effect, but here for some reason it doesn't work for me. It also feels like he really wanted to write this in first person, since we get BC's internal monologue. As it is it's written in kind of a 3rd person limited.
My biggest beef with the story is that it's listed as a science fiction adventure. There's definitely a science fiction element, but I never got a sense of adventure. The story of an assassin, particularly one that's being used by the Vatican in a war torn future, should be action packed. Approximately a third of this story is dedicated to his imprisonment and subsequent theologically based brainwashing. The few times there is action it feels glossed over. This is less James Bond or even Dan Brown than it needs to be.
There's a fair amount of strong language, itself not something I ordinarily object to, but for some reason it was particularly jarring in the second half of the story.