Your premise that it's just fantasy without foundations is subjective. I have read all Sitchin's bibliography and find the Anunnaki idea of our history the most in line with my own observations ever since I was a kid. So I did not had to be convinced of anything.
As for the book, I liked their different take on the Anunnaki, although they focused on very niche part of the written history and had a different take on the events. By talking only about the garden of eden, they did not have to delve into what came before it, so they avoided the "aliens" controversy. They did the research and translations, so it's not yet another armchair warrior type of thing, like Tellinger, for example. And their interpretation does not go against what Sitchin wrote. It's just different take on it, well worth reading if you are a fan of Anunnaki stuff.
Since you mentioned Daniken, he is a sensationalist. Sitchin is, well was, a scholar. They are not playing on the same field and should not be even compared. Daniken is great to read, don't get me wrong, but he uses a lot of fantasy and "what-ifs" and sensationalism. Sitchin on the other hand was a researcher that did the ground work, he did the travelling, he did the translations and he always backed up everything he claimed.
If you want to get the book, I bough it at goldenageproject.org.uk because it is extremely expensive on Amazon. This is an independent reprint of it. But I would recommend to first read Sitchin, he's the foundation for everything else. No one else has done more research and delved as deep as he did. Although after 12th planet, the books become too technical and observational. Less story telling and more describing which does not read to well. If you get the Sitchin bug after 12th planet, go for it. There is a nice set called the complete earth chronicles. Or you can get the summarized version the anunnaki chronicles.