Beauvallet is set in Elizabethan times. I'm not aware of any other Georgette Heyer book that is set in this time, so that makes it a treasure in itself. Nick Beauvallet is a rugged charmer with an eye for a pretty lady--so different from the other Heyer books where the heros are more intellectual and less down to earth. He's a self-made entrepeneur who also happens to be a pirate for England. It's wonderful how Drake and other famous historical characters are mentioned casually as contempories of Nick. Secondary characters steal the show very much like Heyer novels set in Georgian and Regency times. Joshua, Nick's sidekick is delightful. Nick's lady love is a feisty Spanish beauty who is worth the risk that Nick takes to rescue her from an arranged marriage in Spain during the time of the Inquistion. King Philip is a baddie as are his minions who are determined to impose their un-Christian version of Christianity on the general populace (or else!) The outrageous Nick Beauvallet outwits King Philip and his posse in an exciting narrative. You'll enjoy every minute of this old-fashioned but fun book.
It's a rowdy and earthy book, very different than her Georgian/Regency books, which is not a bad thing. If I were to compare it with her other books, I would say it is most like The Talisman Ring in down-to-earth tone. I was surprised and delighted to discover it.