I understand, there is indeed a large difference between Orthogonal and the rest in the sense that it might be technically a fantasy series instead of hard scie

I understand, there is indeed a large difference between Orthogonal and the rest in the sense that it might be technically a fantasy series instead of hard science fiction. However, the exploration of the alternate physical laws gave me the same thrill that other hard science fiction evokes. In some sense, the changed mechanics gave me more insight into physics as a whole (especially with Egan's fantastic online appendices, which might be my favorite aspect of his style). I forgot it above, but I think Incandescence is the "our universe" counterpart to Orthogonal and it is quite good.