Check out the UNH Franklin Pierce Law Library's Library Search for more books and ebooks on this topic. These survey texts will provide you with an overview of the basic premises of international law.
Websites
Revised every six months, this is an excellent textual discussion of how to do international legal research on the Internet, highlighting important primary and secondary sources.
Law Library Resource Xchange –LLRX.com
This site includes a number of research guides on international law posted by law librarians as well as a search function.