If I'm not mistaken, that's a real book called Arthuriana: Early Arthurian Tradition and the Origins of the Legend by Thomas Green:

The origins of Arthur are always going to be controversial.
Given the above conclusion that there is no reason to believe
that the concept of Arthur as a 5th-6th-century warrior is
anything other than a secondary development of the
legendary/mythical Arthur seen in (for example) Preideu Annwfyn,
Pa gur yv y porthaur?, Historia Brittonum Chapter 73 and
Culhwch ac Olwen, the origins of Arthur are essentially open.
While many theories of origins, each internally consistent, can
and probably will be constructed, at present there are two main
theories for the origins of any legendary Arthur.

The rest of the text is available here (skip to "The Origins of Arthur" section).