2.5 Stars --> 3 for the story, 2 for protagonist being such an obnoxious twit (albeit well-intended, but still annoying).
16 yo Gray has a pretty good life, partying with his friends, a part-time job at the local cinema, and occasionally getting the chance to fondle his girlfriend's breasts.
Maggie is his 12 yo sister. She begins to deteriorate from a healthy pre-teen to having significant problems. She limps, bruises easily, develops lumps under her skin, and has to start writing with her other hand. Her parents variously write off the symptoms as growing pains, getting ready to start having her period, ganglion cysts, and the flu. By the time they finally get around to having her seriously checked out, it is Stage IV cancer and she doesn't have a prayer of surviving.
Mom goes totally into "let's try anything to save her life no matter how off the wall it is" mode. On the other hand, Dad the scientist essentially say "she's screwed so let's just let her enjoy the time she has left doing what she wants." Gray starts doing research on her cancer, then starts reciting his latest findings on every known carcinogen and what changes they need to make in their lifestyles. Mom generally sides with Gray, running off to buy new deodorant and shampoo, converting to a macrobiotic diet, etc. Dad is generally disgusted and thinks they're over-reacting. The conflict between them increases as Maggie's condition worsens.
Gray decides he has to live a zero-impact lifestyle, so he quits his job and drops out of school to work on a farm and live in a tent. He becomes a quasi-celebrity with several profiles about his lifestyle, but only sees his sister once a week. As she gets closer to terminal he moves back home and gets reinvolved with her care. Eventually, the inevitable happens.
My ojections against Gray:
1)He is a hypocrite, because his motives aren't that pure. He makes a big deal out of how he's living his zero-impact lifestyle, then makes exceptions when it is convenient (such as when he wants to go on-line). When he receives publicity, his concern is whether he'll look like a hunk on tv so that girls (like his ex-girlfriend) will now want him.
2) He sees everything as being black or white. Either it is wholesome and pure or it kills you. His dad is a scientist and tries to explain the parts per million (or billion) and relative risk of chemicals, but he blows dad off because he is all-knowing. "If it has any risk at all it is bad, therefore we must stop using it because I say so." Just about anything can cause cancer in lab animals if you give them hundreds of times the amount of something that humans would ingest. I remember one scientist who, just to prove his point, caused cancer in rats by putting dimes under their skin, and jokingly argued that money causes cancer and needed to be regulated.
3) He is clueless. What kind of an idiot tells the mother of a dying child that she is responsible for the child developing cancer? He claims he feels bad about it but that he had to tell his mom that the chemicals she works with are known carcinogens (and implying that therefore it's mom's fault that his sister is dying).
4) He is self-centered. He knows his sister is dying and only has a few months to live. So naturally it's more important that he quit school and go flouncing off to pull his Walden routine and only come by to see her once a week. When he's there he can see his mom is struggling to keep it together, so his idea of being helpful is to tell her she needs to start composting. He needs a clue-by-four to the head.
My other objection was that there was no discussion or recriminations about the parents waiting so long to seek treatment for Maggie. They argue all about what they're going to do for her now, but they never discuss whether they failed her by not aggressively trying to find out what was wrong with her. It may not have made a difference in the end, but I can't believe they never thought "if only..."