Years back, I scanned through a few pages and realized it needed effort as you mention.
OTOH, I think there are 2 kinds of great books: one which just suck you into their world and other which demand effort/tax to pay to immerse in that world. The former are incredible books, while the latter are still great.
I found `On Lisp` by PG in the same latter category though GEB and OL tackle different subjects.