Hoppers

Colin Nicholson, student, jack-of-all-subjects and master of only one-English-has nothing much going for him. His widowed mother spends more of her time auditioning for roles in plays and low-budget cable movies than providing decent guardianship. His one solace is the movies, and when a girl named Leanna steps out of the screen one day, claiming that a maniac is chasing her and she needs his help, Colin has no choice but to go along with her, especially when his best friend is blown away by the maniac called Nails. Leanna is from another futuristic Earth, one with interdimensional capability, and Nails and others are after that technology, as she's the only one who knows the secret behind it. Colin's journey with her begins, and their travels range from going to other Earths to a Hell Earth, to a beautiful but deadly beach world.  Along the way, Colin figures out that there's more to the story than meets the eye, and instead of running from their attackers, he and Leanna decide to do their own investigating and meet the attackers head-on. Meeting them head-on seems suicidal.
If he and Leanna lose, then the fate of Earth-all Earths-may end up in the hands of a madman.  However, Colin's mantra is rule or drool. In real terms, it means fight or die. And if it comes to that, he intends to go down swinging.