I recommend Jan Narvesons "the libertarian idea" where he uses the assumption that we all want to live, to derive libertarian ethics based on a contractarian approach. Especially section 2 of the book is good. Section one is too theoretical, 2 is great, and 3 is the application of his ideas to various problems such as security, the environment etc.
Contractarianism says that what is ethical, is what rational beings would agree to in a contract (more or less).