Harnessing — D.J. Manly

Angus has never known freedom. He was born into a world overtaken by aliens who drank the blood of humans. Only Doctor Often offered hope for survival, and every day a fascinated Angus would sneak into the caves to watch the brilliant man tinker in a laboratory with its menagerie of gadgets, glued-together test tubes, and frayed wires.

Then one day, Angus goes home only to discover both his mother and little brother missing. Alone, he returns to Doctor Often, who trains and mentors him. As time passes, Angus and the doctor build their underground community, rescuing humans while food sources dwindle for both aliens and humans alike. Meanwhile, they also work on a steam engine that will one day, hopefully, allow them to build a flying machine to fight their overseers in the sky. But even though steam is the necessity to their possible survival, it's also in dreadfully short supply.

When a blood-drinker named Shylar surprisingly surrenders to Doctor Often and his followers, he says he can supply them with steam, claims he holds the key to defeating his own race, and will help them restore the world to the remaining humans. But can Angus and the doctor trust one of their world's bloodthirsty captors, even if Angus has seen the compelling and alluring vampire in his dreams? Is Shylar leading them all into a deadly trap, or is the beautiful, mysterious alien their dark angel?