The book, Mind Dimension, elucidates how the 3D physical world you experience right now is not the real world that your brain-mind system makes you believe it is. The world with perceived aspects of matter, space, and time, is but an abstraction composed of your own consciousness in the Mind Dimension. Furthermore, the abstraction is not a true representation of the characteristics of the real world in the Real Dimension. It is after all a virtual-reality world, hence the abstraction of the world is based on the way we are designed to experience the world. Other life forms experience the world differently.
The world in the Mind Dimension appears to be real, with physical, spatial and temporal characteristics, however, they are merely virtual-reality mind characteristics—the appearance of 'realness' is an illusion. Also, the world appears 'objectively external' to the so-called 'self' (perceived-self), but it is not. It too is an illusion. All these issues are elaborated upon in the book.