Oh, was this a fun read! Considered one of Heyer's historical romances, I'd argue it has a much stronger mystery plot than anything else (which of course makes me happy).
Unscathed from the wars, Gervase Frant finally returns to his father's estate to claim his title as the new Earl of Stanyon. But his stepmother's resentment and his half brother's open disdain put a chill on Gervase's welcome. Now he must establish himself as the new head of the house and ignore his family's rising hostility.
But Gervase begins to find himself the victim of repeatedly cruel accidents. Soon it becomes increasingly clear that someone wants the new Earl of Stanyon dead. There are shades of Mrs. Bennett in Gervase's step-mother that had me chuckling under my breath as I read, and Gervase himself was smooth as silk, level-headed and the kind of alpha male that doesn't need to assert his alpha-ness, he just is. Miss Moreville is an excellent character as well; wonderfully level-headed and not the last bit silly or 'romantic', while Martin is the male personification of silly and romantic.
The mystery itself was truthfully not really mysterious; Heyer was too heavy-handed for the ending to be anything but obvious, and not a little tragic, but I loved what she did with the rest of the story and the characters; everyone got what was best for them, if not what they wanted. In an oeuvre that covers the spectrum of quality writing, The Quiet Gentleman definitely sits nearer the top. I hope my luck continues with my next Heyer read.