Originally Posted by Dazrin
The 1632 series by Eric Flint (Ring of Fire?) also has a lot of books and is still going. I haven't read it yet, so I don't know how much revolves around a central cast though.
The 163X/Grantville series is more of a shared world project than a traditional series.
There are at least 4 distinct series/narrative arcs in there; the "core" series starring Mike Stearns and family (1632, 1633, 1634 Baltic War, 1635 Eastern Front, 1636 Saxon Uprising), the Vatican Arc (1634 Galileo Afair, 1635 The Cannon Law, 1635 Papal Stakes), the Hapsburg Arc, the new russian Arc, with more to come). And then there's the Ring of Fire Anthologies and the Grantville Gazette short story collection as a sidelights exploring the rest of that universe.
Lots of fun and highly recommended for anybody with an interest in alternate history.
Or real history for that matter; counter-factual history provides a nice counterpoint to better appreciate the past.