Lady Charlotte and the Lending Library by Angelina Jameson

Lady Charlotte and her friends Edith and Louisa are misfits of the marriage mart. Thorne’s Lending Library is their sanctuary from the ton, where they can pursue unconventional hobbies. When Thorne’s is threatened with closure, the three friends band together to save the library.
Lord Ashford must learn whether his sister is satirized in Caroline Lamb’s upcoming novel. An encounter near White’s diverts the marquess from his mission as Ashford becomes involved with Lady Charlotte’s plan to save Thorne’s. He soon discovers the campaign to close the library was instigated by the Rogue’s Alliance, a mysterious London criminal coalition.

As Charlotte and Ashford spend time together, Charlotte discovers that first impressions aren’t always to be believed, and Ashford begins to think the lady isn’t as unsuitable as he first imagined.