Fakery?

[oshfdk]

As much as I'd like the book to be authentic, I understand that if it were, there is nothing of real value to be learned from it. 

I think this is subjective. I probably cannot learn anything of real value from a modern monograph on quantum mechanics. On the other hand, I feel I've learned a lot about thinking and analysis by casually reading some 300-500 year old science books. The modern empirical framework in hard sciences gives us most of the answers, and now by going back to see how people were looking for these answers back then, you can learn a lot about that thinking process in general.

Regarding your estimations of effort, one thing I think is certain: some people have spent more effort trying to make sense of the manuscript than the original author put into making it, and if you compare the group effort, it's not even close 

So, if hundreds or thousands of people chose to spend hours, days, weeks, months, or years deciphering it with no clear personal benefit, it's certainly possible it was created with no personal benefit in mind. I think many authors just create for the sake of creating.