Astraea by Jane Stevenson
Set in the Netherlands in the 1640s, Astraea tells of the relationship between two royal exiles, Elizabeth of Bohemia, daughter of James I, and Omoloju/Pelagius, erstwhile heir to the Yoruba kingdom of Oyo, now a freed slave with shamanic gifts. They meet, fall in love, and marry clandestinely. Secretly, Elizabeth gives birth to a bay Balthasar Stuart, whom both come to see as a hope for a new age. As ever with Stevenson's work, Astraea appeals to both the head and the heart. An utterly convincing picture of seventeenth-century life and politics, it is also an immensely moving account of a strange, magical love affair.