In no particular order:
Julie Anne Long (historical): How the Marquess Was Won. AND A Notorious Countess Confesses. I love almost anything Julie writes. Her dialogue, humor and characterization are absolute best in the field.
Mary Balogh (historical): Slightly Scandalous. Nobody does Victorian romance better than Mary. The mannerisms, the pattern of speech, the dreaded quizzing glass…
Lisa Kleypas (historical): Love in the Afternoon. I do love Victorian/ Regency books about letter-writing, as an epic letter-writer myself.
So these are my favorites, which might change depending on my mood and day, but these books and authors I read over and over and over.
Check them out and let me know what you think!