"Luke the beloved physician greets you, as does Demas. Give my greetings to the brothers at Laodicea, and to Nympha and the church in her house. And when this letter has been read among you, have it also read in the church of the Laodiceans; and see that you also read the letter from Laodicea." - Colossians 4:14-16 ESV
A few thoughts come to mind as I read these last passages of this letter.
What happened to the letter that was written to Laodicea? What did that letter contain? It just didn't survive and get added to the canon of scripture. Still, We don't see scripture as incomplete because God preserved what He wanted preserved.
I think most of the world is looking for something more but more doesn't fix things. More can just complicate life.
I do like that the writer asked them to share this letter. He was humble but he also knew the value of what he was communicating.
I am very happy with the Bible. I don't want more. I read other things but I have no illusions that one day I will find something that will solve all of my problems.
God solved my biggest problems at the cross. The solution lies there.
Of course, there is practical knowledge that benefits people in all sorts of other books and literature.
"For what does it profit a man to gain the whole world and forfeit his soul? For what can a man give in return for his soul?" - Mark 8:36-37 ESV
When we get to the end of this life our soul will be what survives the grave and nothing we have learned will give us the ability to buy it back if we are lost.
The book of Colossians gives us Jesus. The book written to Laodicea is lost. What we have is what matters.