His Scholar by Caroline Lee

Some ruins are ancient…others wear kilts.

Miss Olive L’arbre came to this house party planning to hide behind her archaeological journal and avoid dull lords…instead, she’s finding herself repeatedly distracted by Phineas Oliphant. The man is obscenely handsome, owns a kilt he has absolutely no business wearing that well, and—most alarming of all—actually listens when she talks about Roman rooflines. This is not how house parties are supposed to go.
Phineas Oliphant is charming, brilliant, and entirely too interested in a shy scholar who snaps at him over French etymology and absolutely refuses to admit she keeps staring at his sporran. He’s also hiding several rather large secrets.
Including the one about the Roman balls.

When Phineas invites her to a scandalous midnight rendezvous in their hostess’s study to show her something truly spectacular, Olive realizes her handsome Scottish dinner partner writes under a rather stupid pseudonym…and possesses a pair of sphaera she absolutely must examine.