This is a hard to find book that has seen only three printings. It is a fantastic read and much of the information is solid. A true seeker of grail knowledge should read this book with a grain of salt however. First there are only three chapters that are truly dedicated to Otto Rahn. He figures peripherally in many others, but a sentence here or there does not a central mover and shaker make. Otto Rahn did some great research and from what we can surmise of his work, he may have found the grail location or at the very least some important clues.
The book bases much of its' information on legends and hypothosis. Readers of Holy Blood, Holy Grail will find it fascinating. Some issues that I have with the book are that the German Commando who is credited with the finding of the grail (Skorzeny) was already in custody on the Russian Front at the time he is supposed to be in France locating the Grail. So that begs many questions, did the author make a mistake? The Skorzeny story is too proliferate to be completely a hoax, so maybe he was in France at a different time? This just a little sidenote that needs to be investigated. Other issues that I have with the book could be answered by the publishing dates. More information has come forward since its publication that invalidates some of the books claims. The serious reader should take time to double check facts and historical documents. That being said, it is a fantastic read. There are clues everywhere that bear scrutiny. I would love to sit down with the author and pick his brain. There is more here than meets the eye.
A mess of a book about the "real-life Indian Jones" SS Lt. Otto Rahn. Only about 1/4 of the book actually talks about Otto Rahn. As can be expected, many of the sources are dubious. I recommend checking out "Otto Rahn and the Quest for the Grail: The Amazing Life of the Real Indiana Jones" by Nigel Graddon instead of "Emerald Cup." Although also relying on much speculation and questionable sources, Graddon's book is still much better.
The documentary "The Secret Glory" by director Richard Stanley is easily the best source for reliable information on Otto Rahn. It is also happens to be a beautiful and brilliantly put together documentary.
What a shame no one has written the "definitive" Otto Rahn book. I doubt it will ever happen.