Thought

Ones depiction on reality is different from the next person's depiction.

Although, thought to be dreaming, The Protagonist of this story ventures through many perceptions of reality without knowing that they were actually dead and this was them going through what they thought happened, versus what actually happened. Its like a multiverse, but its actually just opinions.

(Author Note: It's hard to explain what this book is about, it'd be easier to just read it)