The Bible is crystal-clear about the Holy Trinity, yet there are many religious groups that reject the Trinity. That’s why we need the Church’s authoritative interpretation.
An atheist mentioned Gleason Archer’s Encyclopedia of Bible Difficulties and commented, “How could God’s word have ‘difficulties?’ What on earth was difficult about God’s revelation to mankind? I mean, he’s God, right?”
This is shallow, unreflective thinking. I can think of a number of sound, logical reasons why such a book would exist:
1. The Bible is a very lengthy, multi-faceted book by many authors, from long ago, with many literary genres (and in three languages), and cultural assumptions that are foreign to us.
2. The Bible purports to be revelation from an infinitely intelligent God. Thus (even though God simplifies it as much as possible), for us to think that it is an easy thing to immediately grasp and figure out, and that it would not have any number of “difficulties” for mere human beings to work through, is naive. The Bible itself teaches that authoritative teachers are necessary to properly understand it:
Nehemiah 8:1-2, 7-8 (RSV) And all the people gathered . . . and they told Ezra the scribe to bring the book of the law of Moses which the LORD had given to Israel.  And Ezra the priest brought the law before the assembly, both men and women and all who could hear with understanding, . . .  . . . the Levites, helped the people to understand the law, while the people remained in their places.  And they read from the book, from the law of God, clearly; and they gave the sense, so that the people understood the reading.
Mark 4:33-34 With many such parables he spoke the word to them, as they were able to hear it;
 he did not speak to them without a parable, but privately to his own disciples he explained everything.
Acts 8:27-31 “And he rose and went. And behold, an Ethiopian, a eunuch, a minister of the Candace, queen of the Ethiopians, in charge of all her treasure, had come to Jerusalem to worship  and was returning; seated in his chariot, he was reading the prophet Isaiah.  And the Spirit said to Philip, ‘Go up and join this chariot.’  So Philip ran to him, and heard him reading Isaiah the prophet, and asked, ‘Do you understand what you are reading?’  And he said, ‘How can I, unless some one guides me?’ And he invited Philip to come up and sit with him.”
2 Peter 1:20 “First of all you must understand this, that no prophecy of scripture is a matter of one’s own interpretation,” (cf. 2 Pet. 3:15-16)
Moses was told to teach the Hebrews the statutes and the decisions, not just read them to the people (Exod. 18:20). The Levitical priests interpreted the biblical injunctions (Deut. 17:11). Ezra, a priest and a scribe, taught the Jewish Law to Israel, and his authority was binding (Ezra 7:6, 10, 25-26).
3. All grand “theories” have components (“anomalies” / “difficulties”) that need to be worked out and explained. For example, scientific theories do not purport to perfectly explain everything. They often have large “mysterious” areas that have to be resolved.
Think of, for example, the “missing links” in evolution. That didn’t stop people from believing in it. Folks believed in gradual Darwinian evolution (rightly or wrongly) even though prominent paleontologist and philosopher of science Stephen Jay Gould famously noted that “gradualism was never read from the rocks.”
Even Einstein’s theories weren’t totally confirmed by scientific experiment at first (later they were). That a book like the Bible would have “difficulties” to work through should be perfectly obvious and unsurprising to all.
4. Most of the rationale of explaining “Bible difficulties” is not from a perspective that they are real difficulties, but rather, to show that purported difficulties really aren’t such. They are usually based on illogical thinking or unfamiliarity with biblical genre, etc. Many alleged biblical “contradictions” simply aren’t so, by the rules of logic.
5. The Foreword of the book by Kenneth S. Kantzer explains its rationale: “[T]he faith of some troubled souls is hindered by misunderstanding the Scripture. They are confused by what seems to them to be false statements or self-contradiction. We need, therefore, to clear away such false obstacles to faith.” (p. 8)
All complex documents have to be interpreted. When human beings start reading them, they start to disagree, so that there needs to be some sort of authoritative guide.
In law, that is the Supreme Court, In Christianity, it is the Catholic Church, following a consistent tradition of interpretation through the centuries. Protestants reject that authoritative interpretation and adopt sola Scriptura, and so create for themselves all sorts of self-defeating problems and unsolvable dilemmas (I’ve written three books about that).
It’s not that the Bible is profoundly unclear. I have always found it to be clear on any given topic I explored. But one has to have a basic knowledge of how to interpret it. The ancient Hebrews thought about things very differently than the Greeks, and that way of thinking must be learned and understood.
The Bible is crystal-clear about Jesus being God, and the Holy Trinity. I compiled several hundred prooftexts about that in the early 80s. Yet there are many religious groups that reject the Trinity.
That’s why we need authoritative interpretation and the notion of orthodoxy: to have a way to determine truths and stop all the relativistic competing interpretations.
The Bible, though inspired revelation, was still conveyed to us through the work of human writers.
My position is that it can be understood relatively easily for the most part by the common man (with just some basic knowledge of interpretation pointers), but that (for various reasons), human beings in fact have come to disagree about some of the major doctrines in it, and thus, a final say is needed, as in many areas of life.
There were always authoritative teachers in the Jewish and Catholic and Orthodox traditions. It was only Protestantism that rejected that.