The Sky-Blue Wolves by S. M. Stirling
"Two generations after the Change, Crown Princess Órlaith struggles to preserve the hard-won peace her father brought to Montival—the former western North America. But the Change opened many doors, and through them Powers strong and strange and terrible came, to walk once more among humankind.
With her fire-forged friend and ally, Japanese Empress Reiko, Órlaith must take up her sword to stop the spread of the mad malignancy behind the Yellow Raja, who has imprisoned her brother Prince John. And from the emerging superpower of Mongolia, the Sky-Blue Wolves of the High Steppe ride once more beneath the banner of Genghis Khan—the thunder of their hooves resounding across a world in turmoil."
Brand new hardcover in dust jacket!