I've read quite a few books concerning the material in "The Source" from authors like Zecharia Sitchin, Erich Von Daniken, R.L. Dione, and Whitley Strieber. With the exception of Whitley Strieber and R.L. Dione (God Drives a Flying Saucer) most of those weirdo author's books about aliens suck and are boring to read. But Art Bell's style is unique, he doesn't go into too much boring details about translating ancient texts and cave paintings, he gets the main evidence and assembles it nicely in a way which enables anyone who isn't an archeologist to understand what he's talking about. "The Source" is a good journey through the unexplained, but if you want a VERY comprehensive study of the material in his book then look in the bibliography in the back of it and check out some of those authors.