The author wrote this book to try to prove that pre-historical Earth received visitors from out of space who helped with the civilizational process.
The thesis itself is very interesting and he shows amazing data to support his theory, but my feeling is that he attributes too much to ETs, as if our human kind could not have come to some conclusions and discoveries by itself. In the end, all boils down to one thing.
In all, it's an interesting book, but I wouldn't go as far as to say it has convinced me.