This book is fiction, published in 1970s. Its about a young British male who captured and sold into slavery in Carthage. A Carthaginian noblewoman falls in love with him and keeps him alive (although she always has her sexual partners killed after one night!) but he falls in love with a Roman girl. Ends with Roman attack on Carthage and his escape with the Roman girl. The Carthaginian woman sacrifices herself for him.
It’s a long shot, but is there any chance you’re looking for Gustave Flaubert’s Salammbo: A Romance of Ancient Carthage? (Flaubert is better known for having written Madame Bovary.) I haven’t read the book myself, but when I search using your description, this book pops up.
From an online review: “Flaubert’s novel is a love story about Salammbo, daughter of the great Carthaginian general Hamilcar, and Matho, a Libyan mercenary, in the time of the fall of Carthage to the Roman Empire. The story is rife with tales of treachery and deceit, much of it spearheaded by the slave Spendius.”
I think I may have posted that last suggestion prematurely! Here’s one that looks like a more likely match: The Barbarians by Francis Van Wyck Mason. The story was originally published as a six-part serial in Argosy Magazine in 1934. It was expanded and republished as a novel in 1954, and has been reprinted several times since with variations in cover art.
From an online review: “Cealwyn, a bold and brawny young Celt from the Cassiterides, becomes the love-slave of a nymphomanic Carthiginian noblewoman, beautiful but cruel Tiratha, but falls in love with her Roman slave-handmaiden, Valeria. With a group of other slaves looking for vengeance, he plots rebellion and escape. Life becomes more peaceful for Cealwyn after he escapes Carthage and the voracious Tiratha, and only has pirates, Roman press-gangs, naval battles and the siege of Syracuse to deal with. Oh, and the frustratingly virtuous Valeria…”
NBC picked up the rights to the book and filmed it as a TV pilot for a series that was to be called The Barbarians. The series was never made, but the film was released as Rivak the Barbarian, starring Jack Palance in the title role. The film is available on DVD under the title Revak the Rebel. The film covered only the first part of the book and made several significant changes, including renaming the main character from Cealwyn to Rivak (or Revak) and changing him from a Briton to an Iberian prince.
“The Barbarians” is the one. Thanks so much, I can’t believe that anyone would know this obscure book. I’m impressed!