Fundamentally it seems implausible (extraordinary claims requiring extraordinary evidence and all) but it's fun to read about, although I have not braved his actual writings to get context (I do, oddly, have a couple of mathematical textbooks that he wrote, however).
The most interesting thing that I saw was his critique of carbon-14 dating. And while I don't concede the central point, it led me down a rabbit hole of realizing that carbon dating is a lot more complex and rule-of-thumb driven than I would have thought, because in the end it relies upon historic atmospheric C14/C12 ratios that we mostly have good information on from ... radiocarbon dating on artifacts of known provenance. That's not the entirety of the story but it was surprising to me that something that is so often thrown out as an example of formal scientific methods in history is so heuristic and complex, rather than a simple application of math and physics.