Bernard of Clairvaux (I believe he is Catholic) On Loving God is a fifteen chapter work on love, on its degrees, and various other elements of true love
Spring, Gardiner – Distinguishing Traits of Christian Character
Trotter Five Letters on Worship and Ministry in the Spirit.
Sermons on Hebrews by Alan Carr
Steele – Love Enthroned is a work on what is love, its different aspects, biblical examples, etc. 23 chs.
Gospel of the Comforter by Steele is a 36 chapter work on the Holy Spirit and different aspects of Him (1897).
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.