Versteeg (the author, Gaffin is the translator) shows clearly that the New Testament writers thought Adam was a historical man standing at the beginning of the human race. He looks at Romans 5, I Corinthians 15, Luke 3, I Timothy 2, and Jude. These are the only places Adam is mentioned in the NT. In all these passages Adam is treated as a historical figure, not an idea. He does a good job showing why a rejection of the historical Adam leads to a twisting of the Biblical view of sin, Christ, and Christ’s work. Gaffin’s forward is excellent. The book is only 67 pages, but well worth the buy if you are interested in this subject.