If there is a down side to these books (12th Planet et al) it is that the points tend to be made over and over. You can either accept what is said with an open mind or not. Even if the assertions are not true they're fun to read. It often reminds me of episodes of the old Dr. Who program (remember the Cyber Men?)
I have always enjoyed reading these books and then checking out the evidence for myself. The pictoglyphs of the pre-native americans are very interesting as well. Maybe we'll all live to see the answer.....
Sitchin's arguments fit very nicely with the history of Sumeria, Egypt, and the Near East that he laid out in his earlier books. Basically, he argues that the Americas were exploited by the gods for the production of gold and other metals such as tin, which the Andean mountains in particular hold in abundance. Metals were refined here and shipped back to the Near Eastern lands long before Columbus ever sailed the ocean blue. Sitchin believes that the Olmecs, of which very little is known besides what has been gleaned from the artifacts they left behind, particularly in the form of large stone blocks representing men of obvious African descent, did indeed come from Africa very early on--in fact, it was the Egyptian god Thoth who brought his followers here when he was displaced by Marduk. While the Olmecs mysteriously disappeared, other societies were formed by white gods and giants from across the sea. The traditions of the diverse Indian groups all shared a common mythology, including the story of a Great Flood; they also possessed amazing arts, technologies, and sciences (particularly astronomy) very similar to those of Sumeria and Egypt. The inadequacy of artifacts in the Americas necessarily hinder any scientist studying their earliest histories, but Sitchin constructs a remarkably compelling timeline in which the story of Mesoamerica fits very neatly into the history he has gleaned of the Annunaki and their relationships with mankind in its earliest days.
Even if Sitchin were dead wrong on everything he suggests, this book would still be worth reading just for the information about the amazing ancient cities and monuments built in the lower Americas that are only now emerging from their jungle tombs. The Olmecs, Toltecs, Mayans, Incas, and Aztecs are more mysterious than the Near Eastern cultures, and the suggestion that men traveled from the Old World and Africa centuries before Columbus is as compelling as it is fascinating. The illustrations in this book are sometimes rather grainy and hard to examine closely, but the images they convey, such as that of the giant stone heads left by the Olmecs, do much to enhance Sitchin's theories. This is thought-provoking, educational, stimulating material.