The Hydrogen Sonata
I must have read this at least three times before but I am either becoming a more attentive reader or really just skimmed through it previously. I got hugely more out of reading it this time around. There was much that seemed entirely new, much that made more sense than before and a much fuller and more clever/complete/complex plot than I previously appreciated. from my earlier, shallow reading efforts.
It does take some concentration to follow the movements of the various culture craft and determine every one’s motivations, but the descriptions of the almost empty girdle world are quite haunting.
A thoughtful, astounding fully rounded tour-de-force of Science Fiction writing. A huge achievement and a huge loss to us all.