Just read this book in one sitting last night. JH (Hoffmeier) represents the conservative end of spectrum by arguing for Historical genre for Genesis 1 - 11(unity of authorship, the four rivers provide a context in time and space, similarities with other ANE mythic stories explainable by independent witness of same historical event), GW (Wenham) attempts a middle ground of 'proto history' (it's not mere fiction because it's responding to 'external stimuli', pastoral concern on the term 'myth', strong theological exposition of Nephilim/Babel/Flood case studies) while KS (Sparks) accepts mythic genre (multiple conflicting authors/sources within Genesis, dependencies on earlier ANE sources which Genesis tried to subvert/resist (against polytheism, Assyrian oppression).
My impression of the debate is both JH and GW dodged the historical questions wherever possible: Was there really a walking snake who spoke? Was creation in 7 literal days? Were the Nephilim off springs of 'sons of gods' and 'daughters of man'? Was there a historical worldwide flood which destroyed the world except for those kept in a giant boat? Historical Adam/Eve? Do people live hundreds of years before the flood? Was the rainbow created as a post-flood reminder? Begs the question: Which part is historical and which part in myth?
Yes, there are important theological and ideological differences, mythic elements do not rule out historical core but the evidence for close structural similarities (birds sent out of ark) and theological differences with other earlier well-known ANE creation stories and flood stories strongly point to dependencies rather than independent memory to same event. Eponymous ancestry, etiologies, numbering of generations all have clear precedents/precursors in other ancient cultures (Athrahasis, Gilgamesh, Enuma Elish etc).
KS takes on board everything astronomy and evolutionary biology tells us about the world and human history. Quotes Augustine about the need to avoid contradicting 'public knowledge' that makes Christianity a laughing stock. The more you engage vigorously with modern archaeological and scientific findings, the more compelling this position appears. His responses to other contributors, thesis by thesis, push the issues that need clarification. Multiple source/authorship seem to explain what we can observe in different versions of creation/flood stories? Were there 7 pairs of animals or just a pair in the ark? Problem noticed: Some animals were sacrificed after the flood so if there was only one pair, certain species would become extinct.
The only question is where does that leave you with 'biblical authority'? How do we choose which conflicting tradition within the same book (e.g. the sin of Ham justifies violence in Canaan versus Abram has Ephron the Hittite as friend) to "carry the day"? You just have to choose in view of what you think Jesus would do. That might work if the New Testament does not have similarly different streams of tradition/sources as well (e.g. white horse conqueror soaking in blood versus the lamb that was slain).
At the end of day, the debate becomes urgent only because science has pushed the boundaries of what we can accept as plausible or not. The ancients would not question the historicity of such narratives. They are taken at face value until it becomes increasingly hard to do so. The more Christians engage rather than avoid rapid advances made in genetics, biology, astronomy and archaeology, the better their understanding of the biblical canon would become.
