If you like Diana Gabaldon’s Outlander, you’ll probably also like….
— Into the Wilderness, by Sara Donati (no time travel, but Claire shows up as part of an interwoven world);
— Island of the Swans, by Ciji Ware;
— Through a Glass Darkly, by Karleen Koen (again, no time travel, but a very lush, eighteenth century world);
— The Winter Sea, by Susanna Kearsley;
— Kingdom of Shadows, by Barbara Erskine;
— Legend in Green Velvet, by Elizabeth Peters.
Any other suggestions?