Divinity, he says, means to be a whole, perfect human being, without hate, prejudice or malice. That is what he believes the disciples saw in Jesus and were genuinely awed by it. Spong says he is awed by it 2,000 years later.
The problem, he says, is that the disciples lacked the facility to express what they had witnessed and felt, and did the best they could by equating Jesus to the perfection of a god. From there, he said, the traditional Christian understanding of divinity evolved.
I haven't read the book. This seems an ahistorical interpretation. Until I get to read the book, we can at least all agree that Jesus existed.