He has written several other Alternate History/Time Travel books, including The Peshawar Lancers and several Terminator books.
Check out B>Conquistador. This is a really cool book set in several variations of California. Sortly after WWII, a Pacific Theater vet accidently creates a gateway to an alternate california that is spareless populated by hunter/nomadic tribes and sets out to form his own country.
One of the top series is Simon Hawke's Time Wars Series.
Both by Eric Flint.
Time Safari by David Drake
Not Time Travel, but Interdimesional is the late, great, Roger Zelazny's A Dark Traveling. This really cool book is dedicated to the teachers who taught his children to enjoy reading.
Jack Womack's Terraplane is well described as "high weirdness." It's a good weirdness.