I did read it two weeks ago if I remember correctly, interesting but doesn't make much sense unfortunately.
a minor point, but the logic behind it is somewhat circular, a world is unreal because it is outside the invariant set, it is outside the invariant set because it is unreal.
major point, no empirical evidence equals nothing proven. though not much these days in physical theories is based on empirical evidence.
ie. at the most abstract level all we do is create theories, then information is formed-not found, eg. math-physics is less abstract than mathematics in this, thus we need to find empirical proof as well.
reality remains undefinable at the level many would like it to be, seeing as everything depends on observers-not necessarily conscious-, all in the end is in relation to something else, how do you separate it without losing meaning?
kudos to you for reading it btw