This is not a classical question of philosophy, it is a recent question and writings on the subject are
not really philosophical, but philosophising. It is a social question as much as anything and plenty of
social scientists and cultural theorists and journalists have their opinion. However, if you want
something short and to the point, from someone with good credentials, there is A. C. Grayling's The
Future of Moral Values(1997), a Phoenix paperback available in Great Britain. The good thing about
this little book is that it sets the question in the wider liberal context of "the good life in the good
society." Peter Singer has written in favour of euthanasia as well.