Infinity: Chronicles of Nick (Chronicles of Nick, 1)

At fourteen, Nick Gautier thinks he knows everything about the world around him. Streetwise, tough, and savvy, his quick sarcasm is the stuff of legends. . .until the night when his best friends try to kill him. Saved by a mysterious warrior who has more fighting skills than Chuck Norris, the teenaged Nick is sucked into the realm of the Dark-Hunters: immortal vampire slayers who risk everything to save humanity.

Nick quickly learns that the human world is only a veil for a much larger and more dangerous one: a world where the captain of the football team is a werewolf and the girl he has a crush on goes out at night to stake the undead. But before he can even learn the rules of this new world, his fellow students are turning into flesh-eating zombies--and he's next on the menu.
As if starting high school isn't hard enough. . .now Nick has to hide his new friends from his mom, his chain saw from the principal, and keep the zombies and the demon Simi from eating his brains, all without getting grounded or suspended. How in the world is he supposed to do that?