The KJV is the word of God- Dr. Kenneth Gentry’s book He Shall Have Dominion is a theology book I encountered while taking a graduate program in reformed theology. Biblical hermeneutics has validity. It’s just that one must not confuse non-canonical writing with what is. It is comparable to real landscape (the Bible) and maps to the landscape (hermeneutics). Theologians like works like those of Augustine’s and so forth. One can rightly say that anything that is not scripture is not scripture, yet that does not mean that books about Bible archeology or getting a driver’s license are not valid for-themselves, nor that commentaries about the Bible or of Bible history are not right.
One mustn’t confuse categories and the validity of content in appropriate categories. It is true that one only needs the Bible and not a list of theology books, yet theology books in a sense may just comprise the disciplined Bible study of others. It can be useful to know where the pre-incarnate Christ appeared in the Old Testament or references to the Savior by the prophets. That’s the sort of thing theologians compile.
The history of the church has had a lot of debate over the meanings of key concepts like The Trinity. It is unfortunate that different opinions arose, yet many find their way into dogmatic theology and hence church doctrine in time. All the denomination differences about infant baptism, communion, rapture date, eschatology, etc. One can read some theology to compare and contrast their content and hold that content up to that of the KJV as well. Using Venn diagrammatic logic as it were. To discover what is right for-themselves. People even have different opinions about the Kingdom of God, when and what it is. Jesus’ statements often seem to be misunderstood by church leaders hence the value of works of theological rectification such as Gentry’s that are the best available.
Theology does not need to be all exhaustive and inclusive; simply accurate so far as it goes in going over content in the Bible. It must not be deceptive through commission or omission; simply faithful and consistent to Jesus and God as expressed in the Bible.