One of the books that I've come across that gets into the development process of the gospels is: Lost Christianities: The Battles for Scripture and the Faiths

One of the books that I've come across that gets into the development process of the gospels is: Lost Christianities: The Battles for Scripture and the Faiths We Never Knew According to that book, there was a fair bit of religious conflict between the gonastic branch and the proto-orthordox (and some others too) with gospels and edits that attempt to discredit the other sects or build up their own narrative that is in agreement with their faith.