Robert Shaw’s short 1 chapter work on God and the Holy Trinity is an excellent collection of observations and verses that defend the Trinity.
Teasley Holy Spirit and Other Spirits is about the Holy Spirit’s effect on the believer as wells as how other spirits (demons) try to affect mankind with specific unholy spirits.
Timothy Lin work of the Fruit of the Spirit is a short 1 chapter work about the Holy Spirit and the fruit of his indwelling in the believer.
Epp-The Devil Exposed is 12 chapters on different aspects of the Devil, demons, Satan, and man. Temptation, trials.
Steele – Love Enthroned is a work on what is love, its different aspects, biblical examples, etc. 23 chs.
In Smeaton – The Doctrine of the Holy Spirit he examines historically what the Bible teaches about the Holy Spirit. This is an old classic work (1862). In the New Testament portion he looks at topics.
The Carnal Mind by Harmon Allen Baldwin is a 30 chapter work on the carnal mind, defining terms, biblical view, what is evil, guilt, pollution, self-denial, oppositon to light, etc.