Georgette Heyer's Regency World.
The blurb says:
Georgette Heyer fans will delight in Jennifer Kloester’s definitive guide to her Regency world: the people, the shops, clubs and towns they frequented, the parties and seasons they celebrated, how they ate, drank, dressed, socialized, voted, shopped and drove. A fun read for any Heyer fan.
Well, I'm partly a Heyer fan. Mostly because I adore taking her Regency cliches (which she may have invented mind you) and twisting them. Because I'm sure a menage never occurred to Ms. Heyer, which is fine, but I do so love them.
I own this title both in eBook and print. It's got loads of history with Heyer novels as references tossed in. I enjoy reading about both--the history and the books. Included in this are fascinating tidbits about the period that are both obscure enough to enjoy and enjoyable enough to put in Regency books as extra background information.
Highly recommended for all Regency fans.