These books are really good. I am so mad cause I can't find the second (City of Ashes). But anyways they are by Cassandra Clare and here is the summary straight from the back of the book.....

When 15 year old Clary Fray heads out to the Pandemonium Club in New York City, she hardly expects to witness a murder--much less a murder commited by three teenagers covered with strange tattoos abd brandishing bizarre weapons. Clary knows she should call the police, but it's hard to explain a murder when the body dissapears into thin air and the murderers are invisible to everyone but Clary
Equally startled by her ability to see them, the murderers explain themselves as Shadowhunters: a secret tribe of warriors dedicated to ridding the earth of demons. Within 24 hours, Clary's mother dissapears abd Clary herself is almost killed by a grotesque demon.
But why would the demons be interested in mundanes like Clary and her mother? And how did Clary get the Sight? The Shadowhunters would like to know......

And here is a link to where you can read the first chapter.. http://www.mortalinstruments.com/COBchapter1.html
it's super good. I really recommend it.

I read this before! It was really good! Did you know that the author, Cassandra Clare usedto write fanfics? I can't find the 2nd book either though I want to read it!

Really? She did? Wow I'd like to read some of those, hehe And you know there's going to be a third book too? Although i still need the second, it's kind of exciting