Most Christians believe that there was essentially only one early church which was later imperiled by false teachings. The New Testament was the developing statement of this early church, and from it grew the whole structure of Christian belief. In this remarkable book, Michael Goulder sets out to disprove this commonly held theory.
This is a powerful book which helped me understand many things which had puzzled me in the Gospels and St Paul's letters. His main theory is that there were deep disagreements in the early Church which have left their mark on these writings. I think it is possible to be convinced by his arguments without valuing the writings less, but there is a risk there that you have to watch out for.