In case you find yourself browsing the out-of-print shelves anytime soon, there are a few of my favorites that I still cling to in tattered paperback editions because no one has been kind enough to reprint them. They are all WELL worth reading.
If you like Regencies--anything by Fiona Hill, particularly The Country Gentleman. I discovered her when I went through my first Jane Austen phase. (Inevitably, if you love Jane Austen, there comes a time when you've exhausted the major novels, the fragments, the juvenilia, and you are BEREFT that she wrote so little. Then begins the quest to fill the void...) Fiona Hill's voice is astonishingly apt and the novels are bright and charming in a very Pride and Prejudice sort of way.
If you are of an Arthurian bent and like mysteries, Phyllis Ann Karr's The Idylls of the Queen is delicious. It's a proper murder mystery, with Sir Kay sleuthing around Camelot to find a murderer, and everyone a little gray about the temples. The brilliant thing is that you can see the end is coming, but this book is about a relatively peaceful interlude before the destruction of Camelot. It is funny without being silly and modern without being anachronistic.
If you loved The Phantom of the Opera, you must read Susan Kay's Phantom. Seriously. Every person I've ever given it to has sobbed. It is delicious and heartbreaking and pitch-perfect. I haven't read it in more than a dozen years and I could still quote lines from it.