Kerry Greenwood’s Phryne Fisher mystery series set in 1920s Melbourne are great fun and meticulously researched. She also wrote a trilogy of Ancient Greek women, Cassandra, Electra and Medea.
Susanna Kearsley’s romantic suspense novels often include a strong historical theme. She’s a dab hand at mixing parallel stories between now and then, although there’s often a paranormal element, which might never t be your thing.
Christie Dickason writes good historical fiction, I particularly enjoyed The Lady Tree, set in 17th century Europe.
Colleen McCullough‘s Masters of Rome series. I haven’t read them, but I know people who enjoyed them greatly.
Again in the sweeping saga vein, Edward Rutherford’s books which start with Sarum. If you like them, you won’t run out of reading in a while.
Bernard Cornwall’s Sharpe novels might appeal if you like Patrick O’Brian. He also writes a series set in medieval Europe - I prefer his handful of historical mystery novels because I’m not a fan of battle scenes, but Cornwall is an excellent writer.
Judith Merkle Riley wrote six excellent historical novels which are still in print. A Vision of Light is a favourite book of mine, loosely based on the life of medieval visionary Margery Kempe.
Another personal favourite is Diana Norman. I particularly love The Pirate Queen. I think that’s out of print, but several of her others are available as ebooks.