To criticize in a negative sense necessitates the self-generating structure of being specific: in what ways does the book fall short, where is it wrong? That doesn't transfer to the wholly positive review. We might ask, in what ways is this book so very good? But the temptation would be to reply: in all the ways. There's a quality to this fiction that I cannot capture in a review. You'll have to read it for yourself to find out what I mean.
If this was a review of a book by an author I didn't generally like I would be interested. However Roberts certainly implies this is comparable to UKLG the best of her existing work, and to I Claudius. If so, I am now very keen to read it.
Incidentally the book is a retelling of The Aeneid; the end bit set in proto-Latium, centred on the local princess whom Aeneas weds.