A Friendship In Ruins by Chasity Bowlin

A witty friends-to-lovers Regency romance

Miss Eleanor Harcourt has spent years managing her brother’s household — and quietly burying her feelings for his closest friend, Mr. Adrian Grant. He was a confirmed bachelor, and she long ago accepted that he would never look twice at his best friend’s sensible, spinster sister.

Then everything changes.
An unexpected inheritance makes Adrian master of an entailed estate — and a man in need of a wife for the first time in his forty years. Determined to fulfill his new responsibilities, he steps into the marriage mart… only to discover that every eligible woman is inevitably compared to Eleanor. Not as clever. Not as steady. Not as kind. Not as her.

He might have continued ignoring what that meant — until a titled gentleman arrives and begins paying Eleanor very pointed attention.
And Eleanor, who has loved him in resigned silence for years, finds herself quietly fuming that it took another man’s admiration to make Adrian finally notice her. Now she must wonder whether his sudden change of heart is genuine…

…or merely a bout of inconvenient masculine competitiveness.

To claim a future with her, Adrian must weigh the greatest risk he has ever faced — the ruin of his long-standing friendship with her brother — against the one woman he can no longer imagine losing.