maybe you can search online and find some undergrad level medical ethics courses at different colleges and find out what book they are using. i know that my school, univ of southnern cali (USC), has one...religion 460.
For my Bioethics course we used "Intervention and Reflection: Basic Issues in Medical Ethics Ed. 7" by Ronald Munson. I thought it was easy to understand, gave lots of viewpoints, covered most of the issues.
The most influential medical ethics text (other than the Roe decision) in the past thirty years is Beauchamp and Childress' Principles of Biomedical Ethics, currently in its fifth edition.
I personally have many issues with the book, but it is the most often quoted source in modern hospital ethics situations (autonomy-beneficence-nonmaleficence-justice, their four principles, are the dominant analytical categories for approaching cases). Singer is great for reading someone you have to hate, but this text is much better for the basic outline.