Greg Roza 
What Is a Black Hole? [PDF ebook] 

Black holes seem like the stuff of science fiction. It’s incredible to think there’s a mass in the universe with such a strong pull of gravity that not even light can escape it. But it’s not science fiction, and there isn’t just one black hole out there. Diagrams and photographs help readers explore concepts that even scientists can’t fully explain yet. This book will encourage future astrophysicists that more is going on in the night sky than meets the eye.