Thanks for your question.
There is considerable evidence.
There are many ancient texts (Egyptian, Hebrew, Chinese etc) that testify to the truth that the Earth tilted in fairly recent historical times (and may have done so even further back in time).
Our book presents the research of Australian astronomer, George F. Dodwell, who analysed the Earth's axis from ancient sources going back thousands of years. Dodwell's conclusion (based on his research) was that around the end of the Old Kingdom period, the Earth's axis was tilted at around 26.5 degrees.
We also put forward the theory that the four shafts of the Great Pyramid indicate that Giza changed latitude by 6 to 6.5 degrees. This would have been a shift of around 20 or so degrees at the pole and, curiously, would have placed the former pole at the centre of the North American and European ice sheets.
We also present compelling evidence that the Giza complex is the result of a preconceived, homogenous plan. Whilst this does not prove the Gizamids were constructed as Recovery Vaults, it strongly suggests that they could not possibly have been conceived as tombs. It tells us that a considerable number of these large structures were required. Furthermore, close analysis of the Great Pyramid itself leads us to the conclusion that whatever was intended to be placed therein was placed in the pyramid from the top (i.e. before the roof of the King's Chamber was set in place).
In one of the Old Kingdom pyramids, tens of thousands of artefacts (pots, vases, plates, tools and other artefacts) were found in two of its many underground galleries, as well large quantities of wheat and barley seed. The very large amounts of these seeds and artefacts, in our opinion, can in no way be considered as symbolic 'grave goods'.
Obviously there is much, much more detailed information in our book.