My Rogue to Ruin by Erica Ridley

The riotous Wynchester family has taken on a new case to expose a forger, but the prime suspect isn't at all what he seems.

Marjorie Wynchester has always let her siblings take the lead when it comes to planning their investigations. But someone in London is trying to pass off counterfeits, and this time she's the only one with the skill needed to find the culprit. Soon, all the evidence leads her straight to Lord Adrian Webb.

Adrian is a roguish scoundrel of the first order, but he never meant to get caught up in a forgery scheme. Especially one that’s snowballed out of control. Now a blackmailer is out to ruin him, and the most alluring woman he's ever met is trying to put him behind bars.
Every time Marjorie thinks she has Adrian figured out, her assumptions turn on their head. He’s a heartless scoundrel. A loyal brother. A smooth liar. A good kisser. Er…wait… Is winning her affections just one more attempt to avoid the law? Or is it possible he’s not such a rogue after all?