This book is amazing. Don't read it!
Actually, you probably can't read it, even if it is in English. You may recognize most of the words. Even many of the sentences may make sense. Once you try to combine those into paragraphs, however, it will probably not gel. And if it does, you'll probably want to throw the book away and wish you had never seen it.
This is not a novel, and not a textbook, and there's not much poetry either. It is more like holy scripture, except not for any particular religion. By all accounts, Schuon believed in a wide range of religions simultaneously.
Schuon thinks that Heaven would from time to time start a new religion tailored to the mindset of people living in that area. After a while, people would have made that revelation into an institution and most would no longer understand it, but they would preserve enough of the revelation that it still had the power to save souls. In much the same way that electricity works pretty well even if you don't understand it, so also religion. But Schuon writes for those who want to understand it, the spiritual engineer student so to speak.
And that is why, if you are religious, you will probably find Schuon explaining how you have misunderstood your religion, not to mention the other religions. If you are not religious, he will dismiss you as more stupid than an animal. So, not a mass market book.
I have found that I just can't read this as a textbook, although I am pretty good with textbooks. I have to stop and listen to my heart all the time. Sometimes he says something that resonates there, as if it made me remember something that I knew very long ago. And when it does, I understand. And when I understand, I remember ... or rather, I don't even need to remember anymore. It changes how I see things, probably permanently.
Madness is not the only danger in books. There is also the danger that something may be understood that can never be forgotten. Read with caution, if at all.