I'm going to suggest The Interior Life, by Katherine Blake. It concerns a woman in our world who begins having astonishingly vivid visions from the points of view of an aristocratic lady and her chief serving maid in a fantasy world. Our heroine is herself a housewife in the early 1990s; she gets to follow along with the serving-maid for homemaking and household organization (in wartime!) in a more medieval environment, and follow along with the lady for heroic rescues and military alliances above stairs. It has very nice parallels between all three storylines. Out of print but worth looking for.