Teranesia is a calmer work than any of Egan's previous works. The first sections of the book deal with the protagonist's early life on a scientific/tropical paradise, moving on, very abruptly, to later years in Canada and then back to the original island.
In this book, Egan replaces long, introspective monologues on the meaning of reality, but unfortunately doesn't really replace it. When a child, the protagonist deals with emotion by alterring the narrative's reality: inventing monsters, completely avoiding mention of his 'guilty secret', and denying what happened to his family. However, for a boy who is supposed to be very inquisitive and clever, these holes just cry out.
Egan's pot-shots at post-modern critical theory - although an admirable aim - again fall wide of the mark, making the author look ludicrous and petty as well as his targets.
The book gets a lot better towards the end, with realistic emotional rendering and science (at last!) getting a look-see. The theory he presents as the central idea is interesting, but not developed enough. Other science and technology just seems to be lobbed on at points, with characters expounding an explanation at ludicrously unrealistic points.
It feels, to me, that this book is actual a novella padded; not cynically, but as an exercise. Egan's style improves, but at the expense of the sense-of-wonder that many people expect of him. Now, just to combine the two...
All in all, a reasonably good read, and some ideas are there. One to be appreciated with the support of his other works, but not standing as high.