Right ill have to try hard to keep this brief cause i could seriously go off on one!
Firstly nothing to do with the daywalkers movie but there were some movies made, but they are nothing compared to the books,
The Books are about the 'Others' and is set in moscow, Others are magic users that draw their powers from the twilight, which is kind of parallel universe that only Others can walk in.
Their are dark others and light others (good and evil) and they have made a truce call the treaty,
There are Light others called the Night watch that police the dark others and make sure they uphold the treaty and there are dark others called the day watch that police the light others in the same way,
Basically the books follow the ongoing fight between them but in my opinion its one of the most original ways of thinking of magic that ive ever read.
The Films were ok but nothing compared to the books. Each book is split into three smaller sections, the first film was only based on the first section of the first book in the series, the second film even though it has the same title as the second book is based on the second and third sections of the first book. they also have changed some key points that make the movies not as good as the book.