My understanding is that much of the book is based on discredited (although I always have to wonder, discredited by whom?) scholarship, so I see it as a fascinating what if--an AU of history, as it were. The ideas contained within are mostly ones which have at some time in the past floated around, so mostly I find myself wondering what the big deal is. It's as if someone wrote a book about Washington and his cherry tree.

My feeling about HP is similar to yours, which is why I don't read the canon but will watch the movies and on occasion read the fanfic--because I've seen the potential in action and sometimes it is spellbinding.