Angels and Demons:

Angels and Demons: What Do We Really Know about Them? by: Peter J. Kreeft
Non-fiction: Religion, e-book
E-book Count: 34
Book Count: 63

This book answers 100 questions that people have had about angels as well as demons. Some are serous, some are silly, one question is basically a  short essay with the answer being 1 word.  
 They do all have serious theological answers, but some are a bit more light hearted in the response.  For example, how to tell if an angel is visiting you in an assumed body or as a vision: offer them food (not devil's food cake) and see if any of it is missing after they "eat" it, or why science can't prove or disprove angels, because they don't reflect light, and so can't be observed.   Most of the highlights that I made in the book, weren't because they were so deep, but because they were so funny.