The world and the not too large cast of point of view characters is well done. The main conceit is that demons or ‘corelings’ manifest from under the earth from a ‘Core’ (the center of the earth) every night. Sunlight is fatal but they are nearly impossible to kill otherwise and the world must work around that. Buildings and property are protected with wards, which are usually carved, but a scratch to the carving or some other small disruption can make it useless, so families and whole villages are killed on a regular basis. A cultural effect of this is an emphasis on early marriage and procreation, because humanity is more or less in constant danger of being wiped out if not constantly replenished. However, this is no excuse for a male writer to have his female character talk about their ‘flower’ so often or even, really, ever.
Also, I was often disappointed in the action scenes. But the small things, like trade being done by Messenger (capital M), who use portable warding circles but are still respected for being willing to be outside at night for weeks at a time. Aspects of matriarchy creeping into societies, because motherhood is more than usually key to a locale’s survival.
Will I read the next one? Maybe. I’m not one hundred percent sold yet.