James Joyce's Elysses is considered by many to be the most important novel in modern literature. Yet, most people haven't finished reading it, and for those who have read the book, few understand many of its allusions, metaphors and references (Joyce once disclosed that he did it intentionally so as to make future scholars labor endlessly on his work). It is the same for Can Tong Qi 《參同契》, considered by many Neidan 内丹 (Taoist yoga) practitioners as a sacred text. The text is rich with metaphors and allusions, dense and complex, even considered by some as "revelations" from higher spirituality. And, many spent endless hours trying to to decipher the texts for their own satisfaction.
James Joyce was both an excellent writer and a good businessman. He was depicted in Tom Stoppard's famous play Travesties as s shrewd businessman who organized drama production, and incidentally had a legal battle with one of his player Henry Carr (with Joyce won the legal battles eventually in real life).
Carl Jung (as well as Lenin and other famous personalities) was also in Switzerland at that time of WWII, and he treated the mental disorder of Joyce's daughter (when Jung failed to cure her to his satisfaction, Joyce was said to put Jung as one of his minor character and made fun of Jung's Anima theory). The relevancy here is that Joyce was familiar with the psychology of the unconscious. And like Jung, he got his fair share of spiritual revelation.
As a more rational person, James Joyce didn't make his Ulysses his book of revelation. He wrote another book for this purpose, and it is called Finnegans Wake (incidentally Jung's book or revelation is his "Seven Sermons to the Dead"). Hence James Joyce's Ulysses continues to be a classic of modern literature instead of a book on spiritual revelation.
Can Tong Qi is on the other hand the definitive book of revelation of Taoist Master Wei BoYang (魏伯陽), now a definitive text on Neidan (Taoist yoga). As a book of revelation (like Joyce's Finnegans Wake or Jung's Seven Sermons to the Dead), it is highly complex with allusions, metaphors and mysterious significations. Depending on one's belief, it can be interpreted as the high (or highest) spirit speaks, or as Carl Jung would suggest, man's collective archetype speaks, and such revelations stand precariously between the sane and the lunatic, the spiritual and the pathological!
Revelation always draws its own disciples (how many and from where differ). It is understandable for Can Tong Qi, but actually FW and Seven Sermons stood the same, and many a fan of Carl Jung considered him a gnostic rather than a scientist after reading (and re-reading and re-reading...) of his Seven Sermons!
So, it is no wonder that there will be some Neidan practitioners who continue to try to find some hidden secret from Can Tong Qi, and no wonder there will be belief that such secret can reveal the final mystery of Tao, longevity, physical immortality and the living/non-living/spiritual world!
On the other hand, from my own reading of many important classic Taoist texts, I noticed that many prominent Taoists in the past understood the nature of revelations, and would try to look at Can Tong Qi from a more rational angle. For example, the famous Taoist Zhang ZiYang (張紫陽) of the Sung Dynasty who wrote the famous classic text "Folios on Awakening to Reality" 悟真篇, wrote the short piece "Reading Can Tong Qi" 读周易参同契.
At the end of his reading, master Zhang wrote:故知修真志士，讀《參同契》不在夫泥象執文。 And Grandmaster of Centering-lineage(中派) Li DaoChun (李道純）of Qing Dynasty further explained as: 修真高士讀《參同契》者，當咀味求玄，必得之也。執文泥象，奚益者哉。 (A student of Taoist (ultimate) reality who reads Can Tong Qi can obtain good advice from slow and careful reading of this mysterious text. However, if he stubbornly tries to dig out clear explanation for every word, saying, metaphor and signification, he will get nothing useful).
All in all, a reading of Ulysses and Can Tong Qi will be beneficial to those who are interested in the respective subject matter, former being modern literature, while later being Neidan (Taoist yoga). But one is advised not to try to dig out every piece of supposedly "hidden secret" inside the texts. And with this I rest my case.