Madeline has spent the entirety of her 18 years inside. She has a rare disease--SCID, an immunodeficiency disease--that makes her allergic to everything. The outside world is deadly. People can't come into the house without a lengthy decontamination. Her books come prepackaged and shrink-wrapped. Her classes all happen via Skype with online tutors. Her friends are her mom and Carla, the nurse who is with her 8 hours a day. 
 And then Olly moves in next door. They communicate through their windows, then by email, then IM. They are an adorable couple, if you can call them a couple when they can't be in the same house. Carla consents, eventually, to brief visits following the decontamination, and Olly and Maddy get closer. There's even kissing (in violation of the NO TOUCHING parameters Carla has set). Maddy is starting to realize just how much she's missing due to her illness, and hatches a plan to truly LIVE, if even briefly. 
 Okay, so the love story is totally cute and romantic and sweet and Olly is a good guy. (view spoiler)[I did see the truth of Maddy's diagnosis long before she did (I kind of expected it was some sort of Munchausen's by Proxy thing from somewhere before we'd even met the neighbors), and was surprised by the health episode in Hawaii; I still think the heart issue from a virus was overdone and expected it to be something normal like a shellfish allergy. (hide spoiler)] Still, teens will love this, especially those looking for another book like The Fault in Our Stars.