Sitchin, the author of a series of "ancient astronaut" books, was born in Russia, raised in Palestine, and graduated from the University of London with a degree in economic history. He worked for years as a journalist and editor in Israel before settling in New York.
Sitchin, like Velikovsky and Däniken, has invented an entertaining story based on belief that ancient visitors from other worlds came to the earth and used their DNA to create humans. His key ideas are based on twisted transaltions of ancient myths and text. According to Sitchin, ancient Sumerian clay tablets reveal that gods from another planet (Niburu, -the Twelfth Planet in Sitchin's screwy cosmology-, which orbits our Sun every 3,600 years) arrived on Earth some 450,000 years ago and created humans by genetic engineering of female apes.
His books are widely read by the sort of people who read those sorts of books.