What other people have wrote about the NT and mystic origins is of no interest, as it is pure unfounded speculation. A simple fact remains, SOME one or more wrote the NT, the question is what was the MOTIVE?
Let me give you my opinion.
The gospels were written about a man called Jesus. He was an enlightened human being(like many before and after him) here to teach us about love and peace and such, which was not symbolic, it was written as a story.
If Jesus did not exist(this brings up the obvious question, if Jesus didn't exist then who was this person? Brian?), the gospels still teach valuable lessons.
It is blatantly obvious they are not symbolic(the gospels), no matter what these other books and no doubt the money driven authors say.
If you have a scholarly book that theorises the motives of the NT, I am interested, hell, I'm interested in why you think the book teaches something else, and what in your opinion is the motive of this something else.
I think Jesus existed, it is only logical. I think he was a man. I think he was taught his knowledge by someone or some beings that had more knowledge then him and who wanted to help mankind(these beings taught others before and after Jesus, for example the prophets of the OT who describe them as not of this world).
The folks who knew and listened to Jesus wrote down what he said, end of. The knowledge was meant to reach and teach us(the gospels).
Paul met perhaps a being that did not have our best interests in mind and he wrote things that have been the catalyst or an excuse to rage wars ever since his pen(or Luke's or whoever) left the paper.
John on his island penned the revelations which have occurred numerous times since his pen left the paper(from Nero, the black death, world war 1/2 etc) without the 1000 years of peace. Believers wait in anticipation everyday now for another end of days event(all mainstream religions contain this crap), which is both controlling and sad and mad at the same time. John was influenced by a being or beings that did not have mans best interest at heart.
The NT is both good and evil, the good is meant to teach us and bring peace to earth, unfortunately the corrupted books after the gospels are there to create the opposite, and importantly used to control the folks that believe it by using fear.
The motive is (in my opinion) both meant to teach us(the good) and to control us(the bad).
I'm wondering and pondering now as to who or what these beings are, as I believe they have and still do influence mankind.
The simple fact remains, this one book influences the world more than any other book in history by far, so either the writer was the greatest genius ever or the knowledge was not of this world.
Sounds crazy, but not as crazy as thinking that Jesus was/is actually God.
Hope you get better soon.