In short, Yes, I would read it
I think you have a really interesting theme to your novel, a 'loss of innocence' theme (essentially what you have created) has been done alot,but, from your synopsis, it seems you have steered away from a typical story and created a different, more realistic approach, . Bereavement is difficult to cope with, people react differently, by far the most interesting of these reactions is the darker reaction, something I experienced myself, and so myself, and many others, will be able to relate Relation is one of if not the most importance factors authors need to include if readers are to empathize with your character. If the reader cant understand the characters thoughts and feelings, and feel whatever the character is going through, how are they going to show any interest in the rest of the novel?
Whilst I think the idea is excellent. Parts of your synopsis aren't entirely (and note that I am only focusing on the negative points - rather than the positive points)
I think the main problem is the lack of conflict. Sure, you have a huge conflict of his siblings dying, but you need a major conflict towards the end that really pushes the character. I like the 'stealing mothers car' idea, but rather than having the character's 'realization' spawn from the crash you need to give your character a more prominent reason. Remember you've just seen your character go through alot of pain, and he has channeled it through drugs/alcohol. He isn't going to give up on his mind too easily. Perhaps his mother finds out about the car stealing, and after a shouting match between the two, the mother expresses her disappointment in her son perhaps saying she wishes it were him who died in the car crash at the beginning and not the other two. This could then lead the character (driven by anger over what his mother said to him ) to attempt suicide. Drastic, I know, but altogether shocking and would be a great reason (assuming he survives the attempt) for the character to realize that life is short, beautiful, and that he needs to change his ways. Just a suggestion - but one that I think would pay off brilliantly, both giving an emotionally satisfying conclusion, as well as adding heaps of character depth to your main character.
My second, and last, constructive criticism, is more advice (as I don't know your writing style or how much character exploration you are willing to take on) but since your character is going to be involved in serious stuff, like drugs, violence..., you need to make sure that the guy isn't unlikable. Get into his head and find what is making him do these things. Express these on the page to allow sympathy to blossom for him. If the reader doesn't like the character then they won't care about the pain he is going through. Perhaps he could have bad dreams of the day his brother and sister died. Another suggestion is to have a sense of progress in the novel. Around the middle, make it seem as if he is slowly getting better, maybe have him seeing a therapist, ignoring his 'bad' friends, getting better grades. Only to have him get dragged back down again.s by his 'bad' friends teasing him and bullying him about being a wuss because he doesn't because he refuses to do illegal stuff with them since he stared seeing the therapist. This would increase sympathy for him, as well as allowing the reader a glimpse of what he is capable of (i.e. getting out of his post bereavement depression)
These are my thought with your novel. A brilliant idea that has the potential to be an outstanding novel. You just need to follow my advice on the conflict, and make sure you include enough development to make your character likable.
I would buy this book if I saw it in shops. When you eventually finish it, send it off to some publishers, you never know, they might accept and you could have a bestseller on you hands! :)
I may only be 15, but both my parents are authors so I am happy to help!
Good Luck with your novel !!!