Heyer is the Queen of Regency Romance. (See below.) <i>The Grand Sophie</i> is her best. An infinitely complex plot, dozens of threads twisted together into an all-is-resolved ending that may be the best in the history of romance. Certainly the funniest.
Jane Austen lived in and wrote about the Regency Period in English history.(early 1800s). Her five romances are certainly the best from that period. (I hear someone yelling 'Bronte sisters!') Today, Regency Romance often suggests romances written more recently, also called 'historical romances,' but set in the Regency period (as are many of Heyer's). Writing about one's own period would today be called Contemporary Romance. That also connotes, today, a romance with explicit sex (not to be found in Austen nor in Heyer).
So, to fully qualify my first sentence, Heyer is the Queen of Historical Regency Romance. And to unqualify, and include even Jane Austen and the Bronte sisters, Sophie is the most remarkable heroine in the entire history of the romance genre. Pass this one up if you think men should always be in charge!