The City Revealed: Book 4 of the Marek series

Independence brings self-determination, but also threats from without and within
The city of Marek rests on newly-independent laurels. Their ties to Teren, the land-locked nation for which they served as sole trade link to the world, are cut; Teren's Lieutenant, Selene, has been expelled, and her seat rests empty in the Marekhill Council chambers.
But Selene, fresh from her political defeat, threatened to return - next time, not with honeyed words or veiled threats, but with armed soldiers and war sorcerers. Last year, the sorcerers of Marek narrowly defeated a single Teren-summoned demon; how might they fare against a dozen or more?
Twisting the already fraying cord of a city under siege, the common people of Marek grow increasingly fervent in their own demands for representation - for a say in how the city is run, and for whom it is run.
Marcia, Fereno-Heir, agrees with the Lower City; they deserve a better say. But much of the Council won't hear of it - and, of course, there's Selene's threat of an army of sorcerers at the city's magical border. Sorcerers that half the Marekhill Council wouldn't even accept as real.
She must work with the sorcerer Reb, her lover, to force the Council to recognise the truth of magic, whilst her sorcerer brother, Cato, rushes to build some sort of defence.
Because if Teren's demons can pass the Cityangel's wards, it'll be the end of them all.
Book 4 of the Marek series
Cover artwork by Tony Allcock