Evie's never known "normal." She bounced around in foster care until her special talents were discovered when she was eight, and since then she's been an agent under protection of the International Paranormal Containment Agency. Her best friend is a mermaid, and she's homeschooled at the IPCA between capture-and-tag assignments. But really, she's a teen who dreams of hanging out at the mall, having a locker, and going out for pizza with friends.
When the IPCA is infiltrated by a supernatural being they can't identify, Evie's whole world is rocked off it's boring old rails. Before it's over she makes a friend, loses a friend, finds herself, and saves the world (while wearing a really pink prom dress).
The book's got a satisfactory completion, yet still leaves itself open to becoming a series. And I'd buy that - I really liked the characters, they experience realistic angst and emotions, and the action (while supernatural and weird) was also believable.