The Gospel of John itself is worthy of all the accolades, and yet John is ideal for learning Greek. The Greek and the English are simple and profound, but the content is so great that the ancients saw the eagle in its flight of the Fourth Gospel.
But wait! The three Epistles of John are simple and yet carry important messages, even though 1 John is the largest of the three.
The Revelation of John the Divine
or
To John
If the reader spends the time, it will be easy to see how God has given John to the world through the Apostle John. The fabric of Revelation reveals the pattern of the Scriptures from Genesis 1 onward, keeping the same logic of the very last book of the Bible.
