Marked is the first novel in the House of Night series, which is a collaborated effort by P.C. Cast, and her daughter Kristin Cast. The novel is set in a slightly alternate universe to ours, where vampires exist and people know about them. The vampires in this series are not particularly traditional to most fiction adaptations. They are more like crosses between vampires and witches. The protaganist is a sixteen-year-old girl named Zoey, who becomes "marked" - meaning that she is going to become a vampire and she is going to have to attend "vampire school", so named a "House of Night". The story goes on from there, with Zoey making friends and enemies, and discovering that she is not exactly an ordinary vampire.
This is one of those series' that came out quickly after the Twilight franchise began to take off. And despite it's suprising popularity, it's actually one of the weaker alternatives. The characters are poorly developed and strangely changeable, not to mention, occasionally just unlikeable. It is very choppy and not particularly well edited - the choppiness may be explained by the multiple authors who are of different generations and interests. As the series progresses, these problems become even more obvious. I know many people that began reading this series, but few that continued to after about book four. It is not that the concept itself is bad, just that it is not executed well and is often gratuitous.
I would not recommend this book nor the series. If you're looking for a vampire fix, I would stick with Stephenie Meyer or Richelle Mead. But if you are not particular about the discussed issues above, it will be acceptable to you.