A power unbound / Freya Marske.

"Secrets! Magic! Enemies to... something more? Jack Alston, Lord Hawthorn, would love a nice, safe, comfortable life. After the death of his twin sister, he thought he was done with magic for good. But with the threat of a dangerous ritual hanging over every magician in Britain, he's drawn reluctantly back into that world. Now Jack is living in a bizarre puzzle-box of a magical London townhouse, helping an unlikely group of friends track down the final piece of the Last Contract before their enemies can do the same. And to make matters worse, they need the help of writer and thief Alan Ross. Cagey and argumentative, Alan is only in this for the money. The aristocratic Lord Hawthorn, with all his unearned power, is everything that Alan hates. And unfortunately, Alan happens to be everything that Jack wants in one gorgeous, infuriating package. When a plot to seize unimaginable power comes to a head at Cheetham Hall--Jack's ancestral family estate, a land so old and bound in oaths that it's grown a personality as prickly as its owner--Jack, Alan and their allies will become entangled in a night of champagne, secrets, and bloody sacrifice... and the foundations of magic in Britain will be torn up by the roots before the end"--