darinka, Adam has described Spong as highly revisionist. Just how revisionist is suggested by the title of one of his books: Why Christianity Must Change or Die. I feel that Spong asks some interesting and worthwhile questions about Christianity. However, many of his answers I haven’t found all that convincing. If you should want to learn more about him, you could start with this Wikipedia article:
http://en.wikipedia.org/wiki/John_Shelby_Spong