Like Gary Jennings' other books (and I've read a number of them), this one is, as far as I can tell, impeccably researched. But more than anything it is a page turner which is just as well because it runs to well over 1000 pages.
It would be so easy for such a long book about the latter days of the Roman empire and the rise of the Goths to become a pretty turgid historical affair, but as ever Gary Jennings has woven together a thrilling story with extraordinary characters. It is always informative and enjoyable, but never high-brow or difficult to read.
If you've read any other books by this author then you'll recognise his style: the unusual main character (in this case a hermaphrodite who lives life alternately as male and female), the collection of grotesque minor characters, plenty of sex and violence and a very healthy dose of historical fact.
It's hard to recommend too highly, and if you like this then you'll almost certainly also enjoy Aztec, Spangle and The Journeyer by the same author.