The name can be translated as 'The daughter of Kaloyan'. It's the second book of a series about the Asen dynasty, which has ruled the Second Bulgarian Empire (1185-1280). To be honest, I liked it much more than the first book of the series, maybe because it was concentrated on a female character - Maria, the daughter of Kaloyan, the famous Bulgarian emperor, who had ruled from 1196 to 1207. Maria of Bulgaria had become the second Empress consort of Henry of Flanders, Latin Emperor of Constantinople. She has definitely been an interesting person and I think it's a pity that we know so little about her...