The movie is based on novels by Sergei Lukyanenko, and it is not exactly a vampire setting, though it features some.
The idea is there is a secret "mage" underground in today's world with Dark and the Light "sides" (), but there is no direct confrontation. Centuries ago both sides agreed on maintaining a balance, because domination of one provokes bloodshed and chaos. So Night Watch is "light side" monitoring "dark side" at night and Day Watch monitors "light side". Vampires must get permits for fresh human blood. The novels rotate about political intrigues, but movie is action and loses most of it and is not that interesting.
I haven't played the game, but those who did mainly complained it is too short and easy.
BTW, It is the first industrial experience like that in Russia, if I didn't miss anyting else.