Yes, you've hit the nail on the head there, Bookman, you are indeed a member of a very small club of the elect who have read Of Human Bondage or even heard of it despite the fact that it was hugely popular, not just in English speaking countries in its day (having been translated into all the major world languages and being particularly popular in Japan) and for years afterwards and despite the fact that Maugham was one of the most popular authors in the world. It's probably no exaggeration to say that at least 50 million people have read it since its first publication in 1915.
To back up my assertion, like most intelligent people instead of saying the first ill-considered remark that comes into my head, it reads thus in the 2012 prospectus of the Folio Society, who will be publishing a new edition of the book in November 2011 : "Never out of print, and widely acknowledged as Maugham's masterpiece, it was listed by The Times as one of the 100 greatest English-langauge novels of the 20th century.
So, so much for 'underestimated' and 'unknown'!!
And I agree, it is a book of truly epic 'perportions'.
A well-researched review full of brilliantly insightful comments. Keep it up.