The UX is so constrained that you had no choice other than to straight up copy: a) a control to hide the table of contents with a semi-transparent strip hover; b) a table of contents with a near-identical layout; c) a "next page" bumper with opacity-on-hover; d) an annotation stream in a third, right-handed column; d) a cute octopus mascot; etc. etc.

That's not to mention the store.

I mean...imitation may be the sincerest form of flattery, but I draw a line at copying Inky the Octopus.