I'm telling you straight away, if you like Michelle Diener and her 19th century spy historical novels, you'd really enjoy Anne Cleeland.
She calls Tainted Angel "regency Mr. & Mrs. Smith" but I'd say, add "Ocean's Eleven" to this mix. Tainted Angel is a delightful regency heist with some pretty phenomenal banter between its main characters. I loved it!
Vidia is a British spy who is suspected of double-dealing. Enter Lucien Carstairs, who is sent to determine if she is indeed a "tainted" angel. What you don't expect is that both have more layers than you can count and that both are deliciously wily. They also have insane chemistry between each other, and that chemistry works against all their plans and is perhaps the only genuine emotion in this whole affair.
Expect quick thinking, tricks and treachery, twists and turns, pretend drama and non-stop action in this absolutely delicious regency spy mystery. Vidia was a delightful minx, and Lucien had some cards up his sleeve as well. The secondary characters were well rounded and also unexpected in their depth, so please don't discount them and their own little games.
Overall, a must read, clever and charming.