You can't go wrong with the previous suggestions. How can broadening ones horizons be wrong.
I would like to suggest
Bryant and May series. Mystery with a more than a tinge of history.
Harlen Coben - Myron Bolitar series, thriller/mystery with more than a splash of romance.
Nancy Springer - Enola Holmes (Sherlock's younger sister) charming and easy reading set in Victorian times. In a way reminiscent of Georgette Heyer IMO but more mystery.
Then there are the incomparable mystery books by Dorothy Sayers, Margery Allingham and Rex Stout. History, Romance and Mystery
I could go on for days. So many wonderful books in the world.
Helen