I got this book by a random chance, in a pile of old books that I got from someone. Before reading I knew that this person is controversial and scientific community is critizing him, but I was curious anyway. After few chapters I gave up. This is unfortunately gibberish mixed with some facts about ancient cultures.
The author is stating that ancients knew how to create airplanes that could do impossible things. One of the proofs is "Vaimānika Shāstra". I checked it quickly on Wikipedia and read some articles in other sources, and it becomes clear that it's not a proof. It's widely debunked. By the way, take a look at Wikipedia entry about this "Vaimānika Shāstra" and check the illustration of this supposedly ancient planes. They look like if someone combined a bird with a building.
Next he is showing us the similarities between the Bible and Popol Vuh, some sacred book of Maya people. And posing a question why there are so many similarities between religions of the world, why they describe the same thing. It must be true then! It was aliens! Well, as you can quickly check it turns out that:
"By the time Popol Vuh was written, the Maya Guatemalans had already been exposed to Christianity"
So it's a no brainer that Popol Vuh shows similar topics as the bible, since Maya people have been influenced by the bible most probably and just put their twist on that.
After noticing few lies and manipulations like that, I stopped reading because this book can't be read even as an entertainment. It does shows you some information about ancient cultures and history, but if you have book spiked with so many lies, it is better to learn from other sources or even don't learn at all, rather than risk accepting as a fact something that is a lie and is laughed at by historians.