"Deadly Cool" by Gemma Halliday
From Goodreads: "Hartley Grace Featherstone is having a very bad day. First she finds out that her boyfriend is cheating on her with the president of the Herbert Hoover High School Chastity Club. Then he's pegged as the #1 suspect in a murder. And if that weren't enough, now he's depending on Hartley to clear his name. Seriously? Not cool.
But as much as Hartley wouldn't mind seeing him squirm, she knows he's innocent, and she's the only one who can help him. Along with her best friend, Sam, and the school's resident Bad Boy, Chase, Hartley starts investigating on her own. But as the dead bodies begin to pile up, the mystery deepens, the suspects multiply, and Hartley begins to fear that she may be the killer's next victim."
I have heard that this is similar to Veronica Mars and I love me some Veronica! Must get my hands on this ASAP!