A time For Love: Catherine Series, Book 5 by Juliette Benzoni

To rescue her beloved husband Arnaud, who has recovered from illness only to be taken prisoner by the Moorish forces occupying southern Spain, Catherine sets off from her native France on a perilous quest.
Always in danger, she survives hardship and cruelty, high adventure and narrow escapes, to reach the heavily-guarded walls of the city of Granada. There she finds Arnaud - but he is now love-slave to the savage but beautiful Princess Zobeïda.
All Catherine's plans seem doomed to failure when Caliph Muhammad, inflamed by the radiant wonder of her body, chooses her as the favourite of his harem ...
Catherine: A Time for Love is the fifth book in Juliette Benzoni's classic series of historical romances - back in print in the English language for the first time in decades.