[sufue]

Simon the Coldheart is one of Georgette Heyer's few non-Regency romances, set instead during the Hundred Years' War. The Open Road-published version of this has dropped to $0.99 at Kindle and Kobo US right now, and it's discountable at Kobo. Note that there seem to be several versions of this, so make sure you get the one on sale.

The multiple versions thing often means it's in the public domain somewhere. But I've checked Project Gutenberg, and it doesn't show up there. I also checked Faded Page and PG Canada, and it doesn't show up there either. So I'm uncertain as to why the multiple versions, but since this particular one is Open Road, which is a reputable publisher, it should be okay.

Kindle US: https://www.amazon.com/Simon-Coldhea...dp/B08RXL6D14/
Kindle US/Smile: https://smile.amazon.com/Simon-Coldh...dp/B08RXL6D14/
Kobo US: https://www.kobo.com/us/en/ebook/simon-the-coldheart-3

Spoiler:

A valiant orphan rises to knighthood—and finds love with an enemy—in this historical romance of chivalry and adventure during the Hundred Years’ War.

At the dawn of the fifteenth century, England is locked in a bitter war with France. Simon, the illegitimate son of Geoffrey of Malvallet, finds a home in the service of the Earl of Montlice. Distinguishing himself on the field of battle, Simon rises through the ranks until he becomes a friend to the Prince of Wales himself. But Simon’s true test will come when he is sent to overtake the French territory of Belremy.

Though Simon conquers the city, the castle proves difficult to penetrate. Coming face-to-face with the beautiful and defiant Lady Margaret, Simon sees in this bold enemy a spirit to match his own. But can he convince this woman of his love when she would sooner die than surrender?