Silence in the library. [Lily Adler, book 2] / Katharine Schellman.

Enhanced descriptions from Syndetics:

Regency widow Lily Adler didn't expect to find a corpse when visiting a family friend. Now it's up to her to discover the killer in the charming second installment in the Lily Adler mysteries.

Regency widow Lily Adler has finally settled into her new London life when her semi-estranged father arrives unexpectedly, intending to stay with her while he recovers from an illness. Hounded by his disapproval, Lily is drawn into spending time with Lady Wyatt, the new wife of an old family friend. Lily barely knows Lady Wyatt. But she and her husband, Sir Charles, seem as happy as any newly married couple until the morning Lily arrives to find the house in an uproar and Sir Charles dead.

All signs indicate that he tripped and struck his head late at night. But when Bow Street constable Simon Page is called to the scene, he suspects foul play. And it isn't long before Lily stumbles on evidence that Sir Charles was, indeed, murdered.

Mr. Page was there when Lily caught her first murderer, and he trusts her insight into the world of London's upper class. With the help of Captain Jack Hartley, they piece together the reasons that Sir Charles's family might have wanted him dead. But anyone who might have profited from the old man's death seems to have an alibi... until Lily receives a mysterious summons to speak with one of the Wyatts' maids, only to find the young woman dead when she arrives.

Mr. Page believes the surviving family members are hiding the key to the death of both Sir Charles and the maid. To uncover the truth, Lily must convince the father who doesn't trust or respect her to help catch his friend's killer before anyone else in the Wyatt household dies.