Thomas Hunter is in debt to thugs. And not just a small debt, but 100,000 dollars, and they are not happy! In an attempt to hurt Thomas one skims the side of his head with a bullet, causing him to black out, and sending him on an adventure to save two worlds at once from a horrible ending, one being threatened by a virus called the Raison Strain, and the other being attacked by Shataiki - violent, batlike beings.
Morality
Thomas needs a big boost of morality, because most of the time he isn't doing the right thing. Morality is most definitely not one of the things this book is focused on, making it inappropriate for young readers.
Spiritual Content
This book is a type of allegory. Elyon is the main god, an omniscient god of love and compassion. His love for his people is called the Great Romance, that chief love from which all other loves flow. In some of the parts of the book, it is very much alike to the story of Adam and Eve in the garden, when the leader of the Shataiki (creatures of deception) tries to tempt Thomas to eat a fruit that will release other Shataiki into the world. Other Earth, in which Thomas finds himself frequently, is a mirror of his own world with the exception that everything, including spiritual beings, are visible. Being an allegory of Christian principles, then, this book is heavily spiritual.
Violence
There is a lot of violence in "Black." Thomas is shot, he is attacked by all manner of creatures, and all other violence makes this book unsuitable for children and anyone who does not like a dark story.
Drug and Alcohol Content
The arms' dealers are running a biological weapon which, in our society, is understood as illegal. A virus mutates from a vaccine and poses a major potential threat to mankind. This sets up the stage for Dekker's next book "Red."
Sexual Content
There is a scene where Thomas kisses a woman he is not married to, "just to keep her occupied". He is also encouraged to pursue a woman to marry her.
Crude or Profane Language or Content
"Oh God" is used casually in the irreverent sense.
Conclusion
I enjoyed this book for the allegory and action, but the violent content is something to watch out for. I would not recommend this to anyone below its intended age-range.