The list of potential readings here is enormous, but a good place to start is the Stanford Encyclopedia of Philosophy, a free online resource that has articles written by experts in the field. The articles are usually pitched to those with little prior knowledge of the topic under discussion: http://plato.stanford.edu/. This encyclopedia also has excellent articles on most of the topics covered in other parts of this book.
The following represent reliable anthologies with good or excellent introductory material written by their editors: Hugh LaFollette, editor, Ethics in Practice, 4th ed. (Blackwell, 2014); David Boonin and Graham Oddie, editors, What’s Wrong? Applied Ethicists and Their Critics, 2nd ed. (Oxford University Press, 2009); Andrew Cohen and Christopher Wellman, editors, Contemporary Debates in Applied Ethics, 2nd ed. (Blackwell, 2014); R. G. Frey and Christopher Heath Wellman, editors, A Companion to Applied Ethics (Blackwell, 2005); James Sterba, editor, Morality in Practice, 8th ed. (Cengage, 2013).
Here are four superb essay collections authored by excellent moral philosophers who are also fine writers: Joel Feinberg, Rights, Justice and the Bounds of Liberty (Princeton University Press, 1980); Thomas Nagel, Mortal Questions (Cambridge University Press, 1979); Peter Singer, Practical Ethics, 2nd ed. (Cambridge University Press, 1999), and Judith Thomson, Rights, Restitution and Risk (Harvard University Press, 1986).