As one who has sought Truth outside of the box (Bible), I will attest that there are some things the non Canon Gospels and Christian books that highlight the Canon Gospels above all other books in the Bible.
The Canon Gospels are written as the Acts of Jesus. His physical teachings as well as physical actions. His words of spirit John 6:63 are to teach us how to pray and how to seek (the Fathers will through the Holy Spirit). The non Canon books go into greater detail of knowledge and spiritual understanding.
One must know that during Christs time with us, many many heard his message. And many followed his instruction of truth (small t). So one must ask, if he taught so much, why 4 Gospels, all saying the same thing. Most scholars will agree that by the end of the first century, there were more than 100 Gospels. So many churches teaching what they had been taught by:
The 70 Jesus sent out (Luke 10:1) were teaching the "Kingdom of God" as well. John saw others teaching that weren't with them. Mark 9:38-41. So there was much going on due to Christs message to others. Mark didn't walk with Jesus and neither did Luke, but we seek out their message in spirit (physical names mean nothing). So titles should not be taken as spiritual truth.
For 25 years I was a devout Orthodox believer. But the last twenty years, I have been reading and praying on those books and scriptures that were circulating in the 1-3 century (Pre Nicene). After all my studies, I see the separation of the "church". What Jesus wanted as a church and what the Nicene Creed gave us. To understand this, one must see the whole picture (of the Gospel) and not just the part that benefits the Nicene creators. If you see something in Thomas as Jesus saying:
Jesus said, "Whoever does not hate his father and his mother cannot become a disciple to me. And whoever does not hate his brothers and sisters and take up his cross in my way will not be worthy of me."
You see it as the world see's it. Hate my mother, you say? Nonsense. But Jesus was speaking spirit, and no one understands spirit unless they have ears (and eyes).
Matthew said it best:
10 And the disciples came, and said unto him, Why speakest thou unto them in parables?
11 He answered and said unto them, Because it is given unto you to know the mysteries of the kingdom of heaven, but to them it is not given.
12 For whosoever hath, to him shall be given, and he shall have more abundance: but whosoever hath not, from him shall be taken away even that he hath.
13 Therefore speak I to them in parables: because they seeing see not; and hearing they hear not, neither do they understand.
14 And in them is fulfilled the prophecy of Esaias, which saith, By hearing ye shall hear, and shall not understand; and seeing ye shall see, and shall not perceive:
15 For this people's heart is waxed gross, and their ears are dull of hearing, and their eyes they have closed; lest at any time they should see with their eyes and hear with their ears, and should understand with their heart, and should be converted, and I should heal them.
16 But blessed are your eyes, for they see: and your ears, for they hear.
The reason the Catholics would not use the other books is because they create a different perspective of who/what God is. But the Bible itself shows that as well, that the OT God and the Father of Jesus is two different Gods.
I'll stop there. But am open to expound or answer any questions.
