David Drake's Books of the Elements series is not historical fiction, but the setting is based heavily on historical elements with fantasy elements added - nature spirits, magic, etc. It's historical fantasy in the same sense that something like Harry Potter is modern fantasy.
There are four books in the series, each based on an element: Fire, Water, Earth, and Air. The story follows a small group who are pulled into a major world-threatening conflict of magical forces: two young men and two young women, a learned elder, and various allies they meet along the way - both human and magical. At first they're largely ignorant of the big picture, and have to struggle both to stay alive and learn enough to make the right decisions.
If you've read Drake's books before and think that sounds familiar, it's because his Isles series could be described much the same way. As I read this series, I regularly had moments of near deja vu, when Hedia acted just like Ilna, or one of the characters was pulled through some magical portal and had to adventure their way back. There are a lot of similarities, enough so that anyone who didn't like the Isles series can safely skip this one too. But if you did like Isles and wanted more of the same, good news - this is it. (With one caveat - there's more sex in this series than I remember from Isles.)
Drake's writing style is descriptive and easy to read. He keeps the plot moving, constantly sending the main characters off to new places and dangers. I never felt the story bogged down. The characters are decently well developed, with plenty of time devoted to each. My only complaint is that they seem a bit too heroic and/or lucky at times, pulling victory out of some pretty crazy situations, but then this is a heroic fantasy so that's par for the course.
The historical elements of the setting are based on the Roman empire circa 30 AD, as stated in the author's note. The fantastic elements are more varied - there are Norse elements, shamanism, nature magic, and I'm sure plenty of other things I didn't specifically identify. Drake makes use of many sources to pull together his world, not least of which is his own imagination to weave them all together.
The Books of the Elements are a solid read for fans of Drake's work. They're not likely to convert anyone who didn't like his other fantasy titles, though.