What The Bible Teaches by R. A. Torrey will help you to understand the deeper things about God (as a Spirit, unity, eternity omnipresence, personality, omnipotence, omniscience, etc.), Jesus Christ (divinity, subordination, human nature, character of, death, resurrection, ascension, etc.), the Holy Spirit (Personality, deity, distinction from Father and Son, names of, work of, etc.), man (his original condition, the fall, present standing, etc.), and angels (nature, position, number, abode, the Devil, the abode and work of the Devil, and our duty regarding the Devil, etc.).