I just finished reading Sorcery and Cecilia and The Grand Tour by Patricia C. Wrede and Caroline Stevermer. I'd been looking forward to reading the books since I first got my hands on The Grand Tour, but I had to wait until I got a copy of Sorcery and Cecilia. I enjoyed the books very much, but I though the first book was definitely better than the second (which I assume was written because the first was so successful).
The novels are set in a Regency England in which magic is part of everyday life. Sorcery and Cecilia is an epistolary novel. The two main characters, cousins Cecilia and Kate, are separated when Kate is sent to London for her debut season. In addition to the usual society drama and difficulties finding appropriate husbands, there are two evil wizards that whose plans need thwarting.
The Grand Tour follows Cecy and Kate on their honeymoons. Because the two take a joint honeymoon, instead of letters the novel is narrated through Kate's diary entries and excerpts from a deposition given by Cecilia. I don't think the story works quite so well without the characters interacting the way they did through the letters.