Just finished book 5.  Very sad by the ending of a few characters stories.  I didn't start reading the series until after the tv show went off the air.  I have found it to be an easy read and I definitely got hooked on the characters.  My wife started nursing school right after she finished book 3, so I can't even talk to her about the last two books, which is totally killing me.  The wait until book 6 is going to be so long.  At least I will get to relive book 2 this April when the show is back on the air.