I have not read it, and "hard science" means to me, that they have no idea of how reality works, so i probably never will. Even the back of the book say reading this will be a hard slog for me.

Not because of any difficulty in understanding hard concepts, but because i have to suspend WAY TOOO MUCH belief to get through the story.

Denying a person/civilization dimensions is an interesting concept, but it doesn't happen. In our world, moving from 3D to 5D doesn't change anything, it is you, changing what you perceive. It was always there.

There is people who perceive much more than the average person. And we tend to call them insane, and lock them away from the rest of us. We, humans, are so sure that we see everything, and so we know everything. It is the basis of our "scientific method".

We get so many things backwards.

Like, as you described the book, we think it goes universe -> dimensions -> us
When reality is actually completely opposite.
YOU -> dimensions -> universe -> you(the part of you playing in the universe)