I never heard of this Kastrup fellow, but it's pretty hard to want to keep reading about an issue so delicate with so heavy-headed a first page. For example, here's a thing he claims we know "about the universe irrespective of theory or metaphysics", an "empirical fact", he declares, "accessible to anyone through simple observation":

"There is subjective experience. This is the primary and incontrovertible."

This statement is a fine way of starting a conversation and far from a silly thing to assume as a first pass.

But what happens if we try to square his claim that what he is presenting "avoids any a priori metaphysical assumption or bias" with the need to clarify what he means by "subjective"? Is subjectivity a means of knowing (from the inside)? The phenomenal aspect of consciousness (a rug appearing redly)? A way of categorizing facts (the domain of what can be seen from a perspective)? All that matters for now is that any of these responses will result in his first Grand Fact being completely different. And, further, that any answer will involve theoretical machinery, however implicit it is to most people.

What if we then step to the next word and argue that the concept of "experience" is both dispensable (we can do all explanatory work without it) and adds to confusion (by muddling causal and justificatory dimensions of our behavior) and that we should replace it with a family of more restricted concepts? So much for incontrovertible.

And what if we keep going with the second clause of the statement and counter that nothing, in general, can be primary and incontrovertible (that all concepts must earn their keep in explanation)?

It would be tedious---but easy---to do this for every one of the "facts of nature" which ground his pretty pompous exposition. It's easy to think this sort of response is just being clever, but being comfortable with everything being up for grabs and being more modest about what we are actually doing is really the only way an issue as hazy and messy as consciousness can be seriously approached. The playfulness used by Dennett or Hofstader, for example, is not just superfluous or "mere rhetoric", but essential for the stage of understanding we're at.

An aside: I was only scanning for modest evidence that the author was aware of and responsive to the complexity of the issue to see if it was worth my time to read further, not that he actually explicitly addresses every possible move! Also, his substantive position, as far as I glean it, can still be interesting. FWIW I personally have idealist sympathies (appropriately construed) and think both subjectivity and experience do earn their keep...so far.