My measure for whether or not I appreciate a book is (usually) whether it stays with me once I close its covers. This book has certainly done that - in a disturbing, oppressive way. The characters and their relationships are dark and subtly frightening, and that's what I found myself contemplating after reading the book. Iris Murdoch manages to create this emotion gradually, sneakily. I wasn't aware at first that this is what I was beginning to feel. On one hand, that mirrors the main character's realisations, which means the writing works really well. On the other hand, however, there are stretches of painfully slow storytelling (including some philosophical discussions that simply bored me - but I hardly ever think this kind of fictional debate works).
If you enjoy character revelations and relationships in unique settings, then I can definitely recommend this book. The actual plot and substance of the story I found negligible.