Question: "Is it possible that more books could be added to the Bible?"
Answer: There is no reason to believe that God would present further revelation to add to His Word. The Bible begins with the very beginning of humanity--Genesis--and ends with the end of humanity as we know it--Revelation. Everything in between is for our benefit as believers, to be empowered with God's truth in our daily living. We know this from 2 Timothy 3:16-17 (NLT), "All Scripture is inspired by God and is useful to teach us what is true and to make us realize what is wrong in our lives. It straightens us out and teaches us to do what is right. It is God's way of preparing us in every way, fully equipped for every good thing God wants us to do."
If further books were added to the Bible, that would equate to saying that the Bible we have today is incomplete - that it does not tell us everything we need to know. Although it only applies directly to the Book of Revelation, Revelation 22:18-20 teaches us an important truth about adding to God's Word, "I warn everyone who hears the words of the prophecy of this book: If anyone adds anything to them, God will add to him the plagues described in this book. And if anyone takes words away from this book of prophecy, God will take away from him his share in the tree of life and in the holy city, which are described in this book. He who testifies to these things says, 'Yes, I am coming soon.'"
We have all that we need in the current 66 books of the Bible. There is not a single situation in life that cannot be addressed by Scripture. What was begun in Genesis finds conclusion in Revelation. The Bible is absolutely complete and sufficient. Could God add to the Bible? Of course He could. However, there is no reason, biblically or theologically, to believe that He is going to do so.