It depends on what you hope to get out of the rating system. Are you doing it for more accurate personal recommendations or for being a reliable recommender of books to others? Or, for weighing in on what books are truly great and truly bad whether you or even most people would personally enjoyed them or not.

As for me, I use it for accurate personal recommendations. I have no problem giving low ratings to books even if I recognize they're well written or of some importance. Also, there's a "not interested" option in Good Reads' recommendation feature for books that I already know aren't my cup of tea.