Possession is a very complex epistolary novel-within-a-novel that uses the titular "possession" to refer to the relationships between co-workers, lovers, and (which was the most personal to me) the relationship between researcher and subject.

Whereas Dumas may have overutilized the melodramatic, Byatt's characters are very complex, dynamic, and far from black/white cyphers. Possession certainly, in the hands of those willing to dig into it, would generate quite a bit more discussion than what might be found in a surface-level book club setting. You might want to reconsider your stance and give it a try. Or if you're just put off by the subtitle, you could try her most recent work, The Children's Book, which certainly takes that title and twists and warps it considerably