The basic premise is that in 1997 the ghosts of the dead came back - and they were malevolent. A third of the population died, government and religions collapsed, and the Church of the Real Truth was the one organisation that managed to find a way to deal with the ghosts. Now, 23 years later, the Church runs the country (I'm assuming it's US set, but I'll be damned if I could tell you why). They seem a very puritan organisation - with Elders and Goodys in charge, and people being put in the stocks for moral infractions.
Our protagonist is Chess, an employee of the Church. She's a witch, and has the training and magical ability to banish ghosts. She's actually employed as a Debunker - the Church will compensate people who are experiencing hauntings, so people make false claims, the job of a Debunker is to find out if the haunting is legitimate (the rarer case) and deal with the ghost if so. The Debunker gets a bonus for disproving a false claim & the claimant gets a (large) amount of compensation for a real one.
But Chess isn't as squeaky clean as her employers would prefer (and to be honest the whole organisation sounds like it's riddled with corruption/hypocrisy). She's addicted to various drugs, and when her drug dealer has a ghost problem he wants sorted out he quadruples her debt (by saying she owes interest too) then calls her in and suggests she "just" takes care of the ghosts if she wants to ever pay him off. Of course, it doesn't turn out to be as simple as all that - there's more going on than initially meets the eye.
The world felt real & gritty - a world of drug-dealers, gangs, enforcers, and magic. Chess is pretty screwed up, victim of a foster system that was overloaded & world that's not really safe for anyone. The whole thing is told from inside her head (close third person, I guess), and I did like her in all her screwed-upness. The supporting cast are also cool - the "big bad" organisaton are a bit faceless (but at this point in what I think will be a 5 book arc I don't think Chess knows much about them - I'm assuming we & she will learn more later), but all the actual characters are well fleshed out. We only see them through Chess's eyes, but often we see more than she does (particularly with Terrible, her drug-dealer's enforcer, who was my second favourite character in the book). And no-one's all nice, no-one's all bad - there's a fair amount of banal everyday "evil" too.
So far this is a pretty unique & well done urban fantasy - I'm definitely looking forward to reading more in this world, I've reserved the next two books from the library already :)