Although S.M. Stirling’s apparently calling these books (Island in the Sea of Time, Against the Tide of Years, and On the Oceans of Eternity) the Island series. Basic concept: something sends the island of Nantucket back to the Bronze Age. Adventures ensue.
Anyway: I recently replaced my copies of the last two books in the series (they somehow managed to fall into a washing machine), so now I’m rereading them. Good, alt-history/time travel fun.