Once I got into this book, I didn't want to stop reading it. Gardner has what appear to be heavy duty credentials, he is "a Fellow of the Society of Antiquaries of Scotland. Distinguished as the Chevalier de St. Germain, he is a constitutional historian, a Knight Templar of St Anthony, and is Presidential Attaché to the European Council of Princes." (from his official home page). What Gardner offers is an alternate history and meaning to fairy tales like King Arthur, Robin Hood and their holy blood heritage that dates back to gods like Dagon, Marduk and ancient cultures like Sumeria and the Scythians. Linguistically, he relates Indian dialects to European dialects, which makes for very interesting parallels in mythology and cosmology. (As an aside, it is interesting to note that Robert Temple and John Allegro use similar linguistic, that is, etymological, analysis to interrogate ancient history in their books "The Sirius Mystery" and "The Sacred Mushroom and the Cross", respectively - I'll blog about these at another time).
For instance, An, Anu, Anunakki, and Danube (might be) linguistically related. Siddhe and shee (as in pict-shee, or pixie) might also be related, not only linguistically but mythologically. Both siddhe (an Indian word an idea) and shee mean something like "shining one" and refers to people with advanced knowledge.
In a sense then, the legend of the Ring Lords is a secret history of consciousness-expansion that dates back to (pre-)Sumerian times.