If you haven't read Cassandra Clare's Mortal Instruments series, you are missing out big time. I love this series. It's a "Young Adult" series, but don't let that scare you away. I would qualify this as a fantasy-ish series - there are werewolves, vampires, warlocks, fairies, and a race of men called Shadowhunters, that fight demons. It's sexy without having outright sex, it's hilariously funny at times, suspenseful at times, and emotional at times. In other words, it's a fantastic series. I would recommend that you start at the beginning, with City of Bones. The next two books in the series are City of Ashes and City of Glass, followed by the newest book, City of Fallen Angels. Now, this is where it gets a wee bit tricksy - there is a new companion prequel series, and only the first book is out so far. It's called Clockwork Angel, and I would recommend you read it after City of Glass but before City of Fallen Angels. There are some characters introduced in Clockwork Angel that will be referenced in City of Fallen Angels. It's not absolutely crucial that you read it in that order, but that's what I would recommend. Incidentally, the two series are going to be staggered in their release dates - the next book, Clockwork Prince, will be coming out in September of this year, and then City of Lost Souls will be coming out in May 2012, and so on. I don't want to give away too much about this one since there would be some major spoilers, but I will say I loved the book, which was no surprise. I will also say that I am always frustrated when I finish one of these and realize I have to wait another six months for the next book.
Also - once you get into the series, I highly recommend you visit http://www.cassandraclare.com/. She has an excellent FAQ section, as well as release dates for the rest of the books. Ch-ch-check it out.