He believes the Sphinx was built by a pre-Ice Age civilization from Antarctica. You can make the call on this one.

In all seriousness, he lures people in by going on podcasts like Joe Rogan's and putting on a front in which he portrays himself as "just asking question", usually with an implicit insult to lamestream archaeologists, who he accuses of being either cowed into submission by the academic complex or too narrow minded to see The Truth. At best he misrepresents the data and conclusions from academic archaeology and cherry picks what arguments he uses: for example, like many archaeological conspiracists, he will claim that lamestream archaeologists can't answer how, say, the Egyptians built the pyramids, which is technically true given that Imhotep unhelpfully neglected to film it but there are a number of perfectly plausible ways they could have. It is the difference between not knowing precisely how somebody got to the grocery store (did they walk? bike? drive? take a bus? any are plausible) and just being at your wit's end trying to figure out how they could have possibly managed it.

I mean honestly, it is big pile of rocks, you don't need Christopher Wren to figure out how to make it not fall over.

Now getting into specifics, Hancock makes a lot of claims and gives a lot of "interpretations". It would be exhausting, though not particularly challenging, to go through and refute them line by line. If there are specific claims you are curious about I will be happy to address them, given that archaeology conspiracists despite their vivid imaginations tend not to be terribly creative and fall back on a handful of tired claims. But I am not aware of a resource like the wonderful 1421 Exposed that I could point you to.

EDIT: I should probably provide some sources. Unfortunately I can't think of much that is as broad as I am talking here (Bellwood's First Farmers is a good one though), so for a somewhat unorthodox suggestion I would recommend Brian Fagan's wonderful lecture series "Human Prehistory and the First Civilisations".