the Night World series by L.J. Smith is a great series...
here's a summary of the first book The Secret Vampire
Poppy's time in the world is coming to an end...or is it? She has been diagnosed with pancreatic cancer for which the prognosis for survival is grim. But there is another world part yet apart from her world of ordinary things. A world which her best friend (whom she secretly loves), James Rasmussen, belongs to. He offers her a very dangerous invitation to life: to join him in the Night World as a made vampire with immortality. The danger is very real, for by even telling her about the Night World, he has broken one of their greatest laws. By offering to make her a vampire he also breaks another law. Lastly he finds he has broken the final and most important law: to never fall in love with a human. Even further complicating things are Poppy's protective brother Phil, and James' fiendish vampire cousin Ash. If she accepts his invitation, she will never age and vampire blood will prevent her from ever becoming ill again. But, she may not long survive her turning, not with all the Night World legally able to kill them both. If she rejects James' invitation, the alternative is a painful death through cancer, and now she has a chance. Which fate is worse, certain death, or a rugged survival with her soul-mate?will there be a sequel?
I'm reading the second book right now its pretty good to!