Clarify that.
Are books on his humanity
alone being sought? Or books on his nature that include content on his humanity? Any book on Jesus by the JWs or LDS will emphasize his humanity, but at the expense of his deity. Bruce Ware has several books on the Trinity and one of them is titled, "
The Man Christ Jesus: Reflections on the Humanity of Christ." I haven't read that particular tome, but his "
Father, Son, and Holy Spirit: Relationships, Roles, and Relevance" is pretty good.
As far as books on the Trinity go, Michael Reeves' "
Delighting in the Trinity" is pretty good, too, but it's not really a theological exposition on the nature of the Trinity but more an application of the Trinity in our lives. I read it this past summer and this Christian of 40+ years found it enlightening, encouraging, and motivating. If you're looking specifically for a theological dive into the Trinity, then Robert Letham's "
The Holy Trinity," and James White's "
Forgotten Trinity" are recommended.