Had I highlighted the thought-provoking and important passages in this book as I read it, it would be almost fully colored. But in a way, that works against itself: there's too much worth remembering to remember much at all. So this will bear re-reading someday. (Fortunately, it is a slim volume.)
The other thing that makes it so hard to summon up the crystals of philosophy is Fowles prose. It weaves and writhes like a honeysuckle vine. I had to read almost every sentence multiple times, dropping out parenthetical clauses, in order to firmly connect subject to predicate to object. Whether this is a feature or a bug, I am unsure.