Why we Believe the Bible by George DeHoff is a book entirely on apologetics, written in 1939 by G.W. DeHoff. The book was written for the average person. It is easy to understand, filled with evidences for the inspiration of the Bible.
Dehaan Angels and Demons is a 4 chapter teaching on Angels, their importance, their dwelling place, angels ministry.
Dehaan Angels and Demons: Their Nature, Origin, Ministry, and Classification is a very short book of 4 chapters on different points on angels and demons.