Soulstealer. The Soulflake Conspiracies: Volume One

Bekka Trevelyan is an arcanist, and the first woman to be made a Gentleman Scholar of Arcany at the University of Kabakak. Her graduate work was in refining a device to measure the potency of the winds of magic. Over her Yule holidays from teaching, she travels east on a field trip to test her theory about the Winds in the true Wyld. Instead, she finds herself swept up in the investigation of a kidnapping of an indigenous woman and her child by a demon that has possessed the body of a tracker.
Tam Warden was a war hero, and then a sort of government enforcer. He gave up rank and fame to marry across class lines. But government isn't done with him yet. He's called back to action to investigate Bekka's claims - discreetly. This is delicate work, because the truth could unbalance the nation. Essa Bateman is a mercenary spy, a hard woman with no attachments and very few ethics. Few, it turns out, is more than 'none.' She sees the ripples of unrest from the underbelly of society, but deciding what to do about them is a different beast entirely.
In a world where gunpowder is manufactured from the souls of executed criminals, and the ultra-rich seek immortality at any price, where children labour in factories and the desperate poor turn to vampirism, where slavery is rampant and gangs rule the streets... A few people are about to be heroes. They just don't know it yet. But maybe, just maybe, the Revolution is coming.