Abject nonsense, riddled with either misunderstandings and/or misrepresentation of simple data, endless circular reasoning, coincidence, and numerology and magical thinking standing in for mathematics (if you pick and choose your sums so as to only produce significant numbers, then you will consistently produce significant numbers, particularly when you're prepared to fudge the numbers, round up and round down where convenient and accept "close enough" as evidence for a numerical system you're arguing is impossibly precise at every level).

The final conclusion they reach would make for a half-decent sci-fi story, but makes for exceptionally poor science married to an even poorer grasp of archaeology and history. It openly ignores its own flaws of logic with the wafer-thin defence that "other theories have big flaws too", and relies on archaeological and mathematical "coincidences" that are, simply put, bullshit. The central premise relies on assumptions about the likelihood or otherwise of life evolving on Earth (plus, again, a load of nonsensical numerology masquerading as maths), and decides that the unlikeliness of it renders it impossible. Despite wasting a chapter deriding creationism, the book's conclusion is creationism by any other name.