Angels and Demons
Reading Peter Kreeft is always a pleasure: his enthusiasm is contagious, his love for God, his good nature and humility in spite of being a philosopher are qualities that should be expected from any writer of books (whose purpose is to get in our minds his version of things).
His book on angels is short, succint, fun, clever as usual, informative, scholarly but not pedantic, and very entertaining. It's one of those books you read in 3 nights (around 150 pages).
You have to keep in mind that this author is Catholic and so you are going to find the Catholic perspective on certain aspects of the Christian faith. Catholic or Protestant you should agree, as is clearly demonstrated in this book, that angels are not myths, that they exist and the exist for some reason which is not meant to be any secret.
I encourage you to know more about the army of angels that God has disposed for your protection and for communicating His purpose to you, that is: if you are willing to be one of His sons or daughters.
Because we all are his creation, but we only become His children by accepting Christ, His Son, as our Lord and Savior (Savior from sin -to those PC oriented persons).