I think that if a person has an illness that they are certain not to recover from and will, in fact, become more and more ill leading up to the end with more pain, losing their physical independance and/or their mind - this kind of thing then, yes I do think that it's right to be able to chose to die before you get to that stage and if your spouse or whoever is willing to help you then it should not be a crime.
I haven't read the book but think I will pop off and buy that later, sounds good.