I will not stop recommending Hancock's books. In many cases they are the only source of excellent photography of ancient constructions.

Furthermore, Hancock is always very careful to separate factual exposition from his speculations.

Finally, he has remarkably often turned out to be right, and his critics badly wrong. The Younger Dryas Boundary comet strike is now mainstream pre-history, supported by excavations as far afield as Chile, South Africa, and Syria. A culture cultivating the whole Amazon basin for at least 1500 years before being wiped out by smallpox 500 years ago is now well established fact, supported by LIDAR surveys revealing hundreds of miles of major earthworks.