“US readers can find this under ‘The Warded Man’.”
NO MAJOR SPOILERS
Every night, demons (or corelings) rise up and will rip apart any animal or human they find. The only protection against these incursions are wards which can be engraved/painted onto any suitable surface. However, they have to be drawn correctly and have to be properly spaced in order to be fully effective. As a result of this struggle, humankind has been reduced from a population of millions in a technologically advanced society to tens of thousands living in mainly small farming settlements. We join the story some 300 years or so after the commencement of this nightly struggle.
I really like this book, not just because the writing style is accessible (it is) and not just because the story is good (it is). There are three intriguing aspects to the novel.